小开

Python

Number of characters: 237

Fully obfuscated function:

from operator import*
def e(s,l=[]):
if s:l+=list(s.replace(' ','')+')')
a=0;o=add;d=dict(zip(')*+-/',(0,mul,o,sub,div)));p=l.pop
while o:
c=p(0)
if c=='(':c=e(0)
while l[0]not in d:c+=p(0)
a=o(a,float(c));o=d[p(0)]
return a

Clear/semi-obfuscated function:

import operator


def calc(source, stack=[]):
if source:
stack += list(source.replace(' ', '') + ')')


answer = 0


ops = {
')': 0,
'*': operator.mul,
'+': operator.add,
'-': operator.sub,
'/': operator.div,
}


op = operator.add
while op:
cur = stack.pop(0)


if cur == '(':
cur = calc(0)


while stack[0] not in ops:
cur += stack.pop(0)


answer = op(answer, float(cur))
op = ops[stack.pop(0)]


return answer

小开

Ruby 1.9

(because of the regex)

Number of characters: 296

def d(s)
while m = s.match(/((?<pg>\((?:\\[()]|[^()]|\g<pg>)*\)))/)
s.sub!(m[:pg], d(m[:pg][1,m[:pg].size-2]))
end
while m = s.match(/(-?\d+(\.\d+)?)\s*([*+\-\/])\s*(-?\d+(\.\d+)?)/)
r=m[1].to_f.send(m[3],m[4].to_f) if %w{+ - * /}.include?m[3]
s.sub!(m[0], r.to_s)
end
s
end

EDIT: Includes Martin's optimization.

小开

C99

Number of characters: 239 (But see below for 209)

compressed function:

#define S while(*e==32)++e
#define F float
F strtof();char*e;F v();F g(){S;return*e++-40?strtof(e-1,&e):v();}F v(){F b,a=g();for(;;){S;F o=*e++;if(!o|o==41)return a;b=g();a=o==43?a+b:o==45?a-b:o==42?a*b:a/b;}}F f(char*x){e=x;return v();}

decompressed function:

float strtof();


char* e;
float v();


float g() {
while (*e == ' ') ++e;
return *e++ != '(' ? strtof(e-1, &e) : v();
}


float v() {
float b, a = g();
for (;;) {
while (*e == ' ') ++e;
float op = *e++;
if (op == 0 || op == ')') return a;
b = g();
a = op == '+' ? a + b : op == '-' ? a - b : op == '*' ? a * b : a / b;
}
}


float eval(char* x) {
e = x;
return v();
}

Function is not re-entrant.

EDIT from Chris Lutz: I hate to trample on another man's code, but here is a 209-character version:

#define S for(;*e==32;e++)
#define X (*e++-40?strtof(e-1,&e):v())
float strtof();char*e;float v(){float o,a=X;for(;;){S;o=*e++;if(!o|o==41)return a;S;a=o-43?o-45?o-42?a/X:a*X:a-X:a+X;}}
#define f(x) (e=x,v())

Readable (well, not really very readable, but decompressed):

float strtof();
char *e;
float v() {
float o, a = *e++ != '(' ? strtof(e - 1, &e) : v();
for(;;) {
for(; *e == ' '; e++);
o = *e++;
if(o == 0 || o==')') return a;
for(; *e == ' '; e++);
// I have no idea how to properly indent nested conditionals
// and this is far too long to fit on one line.
a = o != '+' ?
o != '-' ?
o != '*' ?
a / (*e++ != '(' ? strtof(e - 1, &e) : v()) :
a * (*e++ != '(' ? strtof(e - 1, &e) : v()) :
a - (*e++ != '(' ? strtof(e - 1, &e) : v()) :
a + (*e++ != '(' ? strtof(e - 1, &e) : v());
}
}
#define f(x) (e = x, v())

Yeah, f() is a macro, not a function, but it works. The readable version has some of the logic rewritten but not reordered (like o != '+' instead of o - '+'), but is otherwise just an indented (and preprocessed) version of the other one. I keep trying to simplify the if(!o|o==41)return a; part into the for() loop, but it never makes it shorter. I still believe it can be done, but I'm done golfing. If I work on this question anymore, it will be in the language that must not be named.

小开

Python

Number of characters: 492

Mildly obfuscated function (short variable names, no spaces around operators):

def e(s):
q=[]
b=1
v=[]
for c in s.replace(' ','')+'$':
if c in '.0123456789' or c in '+-' and b and not v:
v+=[c]
else:
if v:
q+=[float(''.join(v))]
v=[]
while len(q)>=3:
x,y,z=q[-3:]
if type(x)==type(z)==float:
if y=='+':q[-3:]=[x+z]
elif y=='-':q[-3:]=[x-z]
elif y=='*':q[-3:]=[x*z]
elif y=='/':q[-3:]=[x/z]
elif (x,z)==('(',')'):q[-3:]=[y]
else:break
if c=='$':break
q+=[c]
b=c!=')'
return q[0]

I think this is relatively easy to understand. It's a pretty straightforward, naive approach. It doesn't import anything, doesn't use regex, is fully self-contained (single function, no globals, no side-effects), and should handle signed literals (positive or negative). Using more sensible variable names and adhering to recommended Python formatting increases the character count to more like 850-900, a big chunk of that from using four spaces instead of a single tab for indentation.

小开

Haskell

Number of characters: 182

No attempt at cleverness, just some compression: 4 lines, 312 bytes.

import Data.Char;import Text.ParserCombinators.Parsec
q=either(error.show)id.runParser t id"".filter(' '/=);t=do
s<-getState;a<-fmap read(many1$oneOf".-"<|>digit)<|>between(char '('>>setState id)(char ')'>>setState s)t
option(s a)$choice(zipWith(\c o->char c>>return(o$s a))"+-*/"[(+),(-),(*),(/)])>>=setState>>t

And now, really getting into the golf spirit, 3 lines and 182 bytes:

q=snd.(`e`id).filter(' '/=)
e s c|[(f,h)]<-readsPrec 0 s=g h(c f);e('(':s)c=g h(c f)where(')':h,f)=e s id
g('+':h)=e h.(+);g('-':h)=e h.(-);g('*':h)=e h.(*);g('/':h)=e h.(/);g h=(,)h

Exploded:

-- Strip spaces from the input, evaluate with empty accumulator,
-- and output the second field of the result.
q :: String -> Double
q = snd . flip eval id . filter (not . isSpace)


-- eval takes a string and an accumulator, and returns
-- the final value and what’s left unused from the string.
eval :: (Fractional a, Read a) => String -> (a -> a) -> (String, a)


-- If the beginning of the string parses as a number, add it to the accumulator,
-- then try to read an operator and further.
eval str accum | [(num, rest)] <- readsPrec 0 str = oper rest (accum num)


-- If the string starts parentheses, evaluate the inside with a fresh
-- accumulator, and continue after the closing paren.
eval ('(':str) accum = oper rest (accum num) where (')':rest, num) = eval str id


-- oper takes a string and current value, and tries to read an operator
-- to apply to the value.  If there is none, it’s okay.
oper :: (Fractional a, Read a) => String -> a -> (String, a)


-- Handle operations by giving eval a pre-seeded accumulator.
oper ('+':str) num = eval str (num +)
oper ('-':str) num = eval str (num -)
oper ('*':str) num = eval str (num *)
oper ('/':str) num = eval str (num /)


-- If there’s no operation parsable, just return.
oper str num = (str, num)

小开

JavaScript (Not IE compatible)

Number of characters: 268/260

Fully obfuscated function:

function e(x){x=x.replace(/ /g,'')+')'
function P(n){return x[0]=='('?(x=x.substr(1),E()):(n=/^[-+]?[\d.]+/(x)[0],x=x.substr(n.length),+n)}function E(a,o,b){a=P()
for(;;){o=x[0]
x=x.substr(1)
if(o==')')return a
b=P()
a=o=='+'?a+b:o=='-'?a-b:o=='*'?a*b:a/b}}return E()}

or, in JavaScript 1.8 (Firefox 3+), you can save a few characters by using expression closures:

e=function(x,P,E)(x=x.replace(/ /g,'')+')',P=function(n)(x[0]=='('?(x=x.substr(1),E()):(n=/^[-+]?[\d.]+/(x)[0],x=x.substr(n.length),+n)),E=function(a,o,b){a=P()
for(;;){o=x[0]
x=x.substr(1)
if(o==')')return a
b=P()
a=o=='+'?a+b:o=='-'?a-b:o=='*'?a*b:a/b}},E())

Clear/semi-obfuscated function:

function evaluate(x) {
x = x.replace(/ /g, "") + ")";
function primary() {
if (x[0] == '(') {
x = x.substr(1);
return expression();
}


var n = /^[-+]?\d*\.?\d*/.exec(x)[0];
x = x.substr(n.length);
return +n;
}


function expression() {
var a = primary();
for (;;) {
var operator = x[0];
x = x.substr(1);


if (operator == ')') {
return a;
}


var b = primary();
a = (operator == '+') ? a + b :
(operator == '-') ? a - b :
(operator == '*') ? a * b :
a / b;
}
}


return expression();
}

Neither version will work in IE, because they use array-style subscripting on the string. If you replace both occurrences of x[0] with x.charAt(0), the first one should work everywhere.

I cut out some more characters since the first version by turning variables into function parameters and replacing another if statement with the conditional operator.

小开

C#

Number of characters: 396 (updated)

(but fails the test you added with "/ -8", and I'm not inclined to fix it...

static float Eval(string s){int i,j;s=s.Trim();while((i=s.IndexOf(')'))>=0){j=s.LastIndexOf('(',i,i);s=s.Substring(0,j++)+Eval(s.Substring(j,i-j))+s.Substring(i+1);}if((i=s.LastIndexOfAny("+-*/".ToCharArray()))<0) return float.Parse(s);var r=float.Parse(s.Substring(i+1));var l=i>0?Eval(s.Substring(0,i)):(float?)null;return s[i]=='+'?(l??0)+r:(s[i]=='-'?(l??0)-r:(s[i]=='/'?(l??1)/r:(l??1)*r));}

From:

static float Eval(string s)
{
int i, j;
s = s.Trim();
while ((i = s.IndexOf(')')) >= 0)
{
j = s.LastIndexOf('(', i, i);
s = s.Substring(0, j++) + Eval(s.Substring(j, i - j)) + s.Substring(i + 1);
}
if ((i = s.LastIndexOfAny("+-*/".ToCharArray())) < 0) return float.Parse(s);
var r = float.Parse(s.Substring(i + 1));
var l = i > 0 ? Eval(s.Substring(0, i)) : (float?)null;
return s[i] == '+'
? (l ?? 0) + r
: (s[i] == '-'
? (l ?? 0) - r
: (s[i] == '/'
? (l ?? 1) / r
: (l ?? 1) * r));
}

小开

C#

Number of characters: 403

So here's my solution... I'm still waiting for someone to post one in C# that can beat it. (Marc Gravell was close, and may yet do better than me after some more tinkering.)

Fully obfuscated function:

float e(string x){float v=0;if(float.TryParse(x,out v))return v;x+=';';int t=0;
char o,s='?',p='+';float n=0;int l=0;for(int i=0;i<x.Length;i++){o=s;if(
x[i]!=' '){s=x[i];if(char.IsDigit(x[i])|s=='.'|(s=='-'&o!='1'))s='1';if(s==')')
l--;if(s!=o&l==0){if(o=='1'|o==')'){n=e(x.Substring(t,i-t));if(p=='+')v+=n;
if(p=='-')v-=n;if(p=='*')v*=n;if(p=='/')v/=n;p=x[i];}t=i;if(s=='(')t++;}
if(s=='(')l++;}}return v;}

Semi-obfuscated function:

public static float Eval(string expr)
{
float val = 0;
if (float.TryParse(expr, out val))
return val;
expr += ';';
int tokenStart = 0;
char oldState, state = '?', op = '+';
float num = 0;
int level = 0;
for (int i = 0; i < expr.Length; i++)
{
oldState = state;
if (expr[i] != ' ')
{
state = expr[i];
if (char.IsDigit(expr[i]) || state == '.' ||
(state == '-' && oldState != '1'))
state = '1';
if (state == ')')
level--;
if (state != oldState && level == 0)
{
if (oldState == '1' || oldState == ')')
{
num = Eval(expr.Substring(tokenStart, i - tokenStart));
if (op == '+') val += num;
if (op == '-') val -= num;
if (op == '*') val *= num;
if (op == '/') val /= num;
op = expr[i];
}
tokenStart = i;
if (state == '(')
tokenStart++;
}
if (state == '(')
level++;
}
}
return val;
}

Nothing too clever going on here, it woul seem. The function does however have the advantage of being re-entrant (i.e. thread-safe).

I am also reasonably pleased with the number of chars, given that it's written in C# (valid 1.0, 2.0, and 3.0 I believe).

小开

Ruby 1.8.7

Number of characters: 620

Do try and take it easy on my implementation, it's the first time I've written an expression parser in my life! I guarantee that it isn't the best.

Obfuscated:

def solve_expression(e)
t,r,s,c,n=e.chars.to_a,[],'','',''
while(c=t.shift)
n=t[0]
if (s+c).match(/^(-?)[.\d]+$/) || (!n.nil? && n.match(/\d/) && c=='-')
s+=c
elsif (c=='-' && n=='(') || c=='('
m,o,x=c=='-',1,''
while(c=t.shift)
o+=1 if c=='('
o-=1 if c==')'
x+=c unless c==')' && o==0
break if o==0
end
r.push(m ? -solve_expression(x) : solve_expression(x))
s=''
elsif c.match(/[+\-\/*]/)
r.push(c) and s=''
else
r.push(s) if !s.empty?
s=''
end
end
r.push(s) unless s.empty?
i=1
a=r[0].to_f
while i<r.count
b,c=r[i..i+1]
c=c.to_f
case b
when '+': a=a+c
when '-': a=a-c
when '*': a=a*c
when '/': a=a/c
end
i+=2
end
a
end

Readable:

def solve_expression(expr)
chars = expr.chars.to_a # characters of the expression
parts = [] # resulting parts
s,c,n = '','','' # current string, character, next character


while(c = chars.shift)
n = chars[0]
if (s + c).match(/^(-?)[.\d]+$/) || (!n.nil? && n.match(/\d/) && c == '-') # only concatenate when it is part of a valid number
s += c
elsif (c == '-' && n == '(') || c == '(' # begin a sub-expression
negate = c == '-'
open = 1
subExpr = ''
while(c = chars.shift)
open += 1 if c == '('
open -= 1 if c == ')'
# if the number of open parenthesis equals 0, we've run to the end of the
# expression.  Make a new expression with the new string, and add it to the
# stack.
subExpr += c unless c == ')' && open == 0
break if open == 0
end
parts.push(negate ? -solve_expression(subExpr) : solve_expression(subExpr))
s = ''
elsif c.match(/[+\-\/*]/)
parts.push(c) and s = ''
else
parts.push(s) if !s.empty?
s = ''
end
end
parts.push(s) unless s.empty? # expression exits 1 character too soon.


# now for some solutions!
i = 1
a = parts[0].to_f # left-most value is will become the result
while i < parts.count
b,c = parts[i..i+1]
c = c.to_f
case b
when '+': a = a + c
when '-': a = a - c
when '*': a = a * c
when '/': a = a / c
end
i += 2
end
a
end

小开

PHP

Number of characters: 284

obfuscated:

function f($m){return c($m[1]);}function g($n,$m){$o=$m[0];$m[0]=' ';return$o=='+'?$n+$m:($o=='-'?$n-$m:($o=='*'?$n*$m:$n/$m));}function c($s){while($s!=($t=preg_replace_callback('/\(([^()]*)\)/',f,$s)))$s=$t;preg_match_all('![-+/*].*?[\d.]+!',"+$s",$m);return array_reduce($m[0],g);}

readable:

function callback1($m) {return c($m[1]);}
function callback2($n,$m) {
$o=$m[0];
$m[0]=' ';
return $o=='+' ? $n+$m : ($o=='-' ? $n-$m : ($o=='*' ? $n*$m : $n/$m));
}
function c($s){
while ($s != ($t = preg_replace_callback('/\(([^()]*)\)/','callback1',$s))) $s=$t;
preg_match_all('![-+/*].*?[\d.]+!', "+$s", $m);
return array_reduce($m[0], 'callback2');
}




$str = '  2.45/8.5  *  -9.27   +    (   5   *  0.0023  ) ';
var_dump(c($str));
# float(-2.66044117647)

Should work with any valid input (including negative numbers and arbitrary whitespace)

小开

Common Lisp

(SBCL)
Number of characters: 251

(defun g(e)(if(numberp e)e(let((m (g (pop e)))(o(loop for x in e by #'cddr collect x))(n(loop for x in (cdr e)by #'cddr collect (g x))))(mapcar(lambda(x y)(setf m(apply x(list m y))))o n)m)))(defun w(e)(g(read-from-string(concatenate'string"("e")"))))

Proper version (387 chars):

(defun wrapper (exp) (golf-eval (read-from-string (concatenate 'string "(" exp ")"))))


(defun golf-eval (exp)
(if (numberp exp)
exp
(let ((mem (golf-eval (pop exp)))
(op-list (loop for x in exp by #'cddr collect x))
(num-list (loop for x in (cdr exp) by #'cddr collect (golf-eval x))))
(mapcar (lambda (x y) (setf mem (apply x (list mem y)))) op-list num-list)
mem)))

Input is form w(), which takes one string argument. It uses the trick that nums/operands and operators are in the pattern N O N O N ... and recursively evaluates all operands, and therefore getting nesting very cheap. ;)

小开

Python 3K

(its 3K because / converts the result to a floating point number)

Number of characters: 808

Clear (I cannot write obfuscated code in Python XD):

def parse(line):
ops = {"+": lambda x,y:x+y,
"-": lambda x,y:x-y,
"*": lambda x,y:x*y,
"/": lambda x,y:x/y}
def tpp(s, t):
if len(s) > 0 and s[-1] in ops:
f = ops[s.pop()]
t = f(s.pop(), t)
return t
line = line + " "
s = []
t = 0
m = None
for c in line:
if c in "0123456789":
if not m:
m = "i"
if m == "i":
t = t*10 + ord(c)-ord("0")
elif m =="d":
t = t + e*(ord(c)-ord("0"))
e*=0.1
elif c == ".":
m = "d"
e = 0.1
elif m:
t = tpp(s,t)
s.append(t)
m = None
t = 0


if c in ops or c == "(":
s.append(c)
elif c == ")":
t = s.pop()
s.pop()
s.append(tpp(s,t))
t = 0
t = s.pop()
if int(t) == t:
t = int(t)
return t

I'm not using any kind of regular expression, even the number parsing is made by hand ;-)

Quite simple, scans the line, it can be in 3 different modes (m), None that means that there's no number being parsed, "i" that means that it is parsing the integer part and "d" that means that is parsing the decimal part.

It uses a stack to store the temporary computations, when it has finished parsing a number sees if it there was an operator in the stack, in that case evals and pushes. The opening parens are just pushed and the closing parens remove the opening paren and repush the current eval.

Fairly simple and straightfordward :-)

小开

F#

Number of characters: 327

OP was looking for an F# version, here it is. Can be done a lot nicer since I'm abusing a ref here to save characters. It handles most things such as -(1.0), 3 - -3 and even 0 - .5 etc.

let g s=
let c=ref[for x in System.Text.RegularExpressions.Regex.Matches(s,"[0-9.]+|[^\s]")->x.Value]
let rec e v=if (!c).IsEmpty then v else
let h=(!c).Head
c:=(!c).Tail
match h with|"("->e(e 0.0)|")"->v|"+"->e(v+(e 0.0))|"-"->e(v-(e 0.0))|"/"->e(v/(e 0.0))|"*"->e(v*(e 0.0))|x->float x
e(e 0.0)

小开

Ruby

Number of characters: 302

Semi-obfuscated:

def e(l)
t=0.0;o=nil
while l!=''
l.sub!(/^\s+/,'')
l.sub!(/^(-?\d+|-?\d+\.\d+)/,'')
t=o ? t.send(o, $1.to_f) : $1.to_f if $~
l.sub!(/^(\+|-|\*|\/)/,'')
o=$1 if $~
l.sub!(/^\(/,'')
t=o ? t.send(o, e(l)) : e(l) if $~
l.sub!(/^\)/,'')
return t if $~
end
t
end

Destroys original string, also assumes expression is well-formed (only valid characters, and matching brackets).

Not obfuscated:

def evaluate_expression(expression)
result_so_far = 0.0
last_operator = nil


while (expression != '')
# remove any leading whitespace
expression.sub!(/^\s+/, '')


# extract and remove leading integer or decimal number
expression.sub!(/^(-?\d+|-?\d+\.\d+)/, '')
if $~
# match was successful
number = $1.to_f
if last_operator.nil?
# first number, just store it
result_so_far = number
else
# we have an operator, use it!
# last_operator is a string matching '+', '-', '*' or '/'
# just invoke the method of that name on our result_so_far
# since these operators are just method calls in Ruby
result_so_far = result_so_far.send(last_operator, number)
end
end


# extract and remove leading operator +-*/
expression.sub!(/^(\+|-|\*|\/)/, '')
if $~
# match was successful
last_operator = $1
end


# extract and remove leading open bracket
l.sub!(/^\(/, '')
if $~
# match successful
if last_operator.nil?
# first element in the expression is an open bracket
# so just evaluate its contents recursively
result_so_far = evaluate_expression(expression)
else
# combine the content of the bracketing with the
# result so far using the last_operator
result_so_far.send(last_operator, evaluate_expression(expression))
end
end


# extract and remove leading close bracket
l.sub!(/^\)/, '')
if $~
# match successful
# this must be the end of a recursive call so
# return the result so far without consuming the rest
# of the expression
return result_so_far
end
end
t
end

The recursive call is controlled by the modification of the expression string, which is a bit nasty, but it seems to work.

小开

Python with regular expressions

Number of characters: 283

Fully obfuscated function:

import re
from operator import*
def c(e):
O=dict(zip("+-/*()",(add,sub,truediv,mul)))
a=[add,0];s=a
for v,o in re.findall("(-?[.\d]+)|([+-/*()])",e):
if v:s=[float(v)]+s
elif o=="(":s=a+s
elif o!=")":s=[O[o]]+s
if v or o==")":s[:3]=[s[1](s[2],s[0])]
return s[0]

Not obfuscated:

import re
from operator import *


def compute(s):
operators = dict(zip("+-/*()", (add, sub, truediv, mul)))
stack = [add, 0]
for val, op in re.findall("(-?[.\d]+)|([+-/*()])", s):
if val:
stack = [float(val)] + stack
elif op == "(":
stack = [add, 0] + stack
elif op != ")":
stack = [operators[op]] + stack
if val or op == ")":
stack[:3] = [stack[1](stack[2], stack[0])]
return stack[0]

I wanted to see if I cab beat the other Python solutions using regular expressions.

Couldn't.

The regular expression I'm using creates a list of pairs (val, op) where only one item in each pair is valid. The rest of the code is a rather standard stack based parser with a neat trick of replacing the top 3 cells in the stack with the result of the computation using Python list assignment syntax. Making this work with negative numbers required only two additional characters (-? in the regex).

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C# with Regex Love

Number of characters: 384

Fully-obfuscated:

float E(string i){i=i.Replace(" ","");Regex b=new Regex(@"\((?>[^()]+|\((?<D>)|\)(?<-D>))*(?(D)(?!))\)");i=b.Replace(i,m=>Eval(m.Value.Substring(1,m.Length-2)).ToString());float r=0;foreach(Match m in Regex.Matches(i,@"(?<=^|\D)-?[\d.]+")){float f=float.Parse(m.Value);if(m.Index==0)r=f;else{char o=i[m.Index-1];if(o=='+')r+=f;if(o=='-')r-=f;if(o=='*')r*=f;if(o=='/')r/=f;}}return r;}

Not-obfuscated:

private static float Eval(string input)
{
input = input.Replace(" ", "");
Regex balancedMatcher = new Regex(@"\(
(?>
[^()]+
|
\( (?<Depth>)
|
\) (?<-Depth>)
)*
(?(Depth)(?!))
\)", RegexOptions.IgnorePatternWhitespace);
input = balancedMatcher.Replace(input, m => Eval(m.Value.Substring(1, m.Length - 2)).ToString());


float result = 0;


foreach (Match m in Regex.Matches(input, @"(?<=^|\D)-?[\d.]+"))
{
float floatVal = float.Parse(m.Value);
if (m.Index == 0)
{
result = floatVal;
}
else
{
char op = input[m.Index - 1];
if (op == '+') result += floatVal;
if (op == '-') result -= floatVal;
if (op == '*') result *= floatVal;
if (op == '/') result /= floatVal;
}
}


return result;
}

Takes advantage of .NET's Regex balancing group feature.

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F#

Number of characters: 461

Here is Marc Gravell's solution (essentially) converted from C# to F#. The char count is scarecly better, but I thought I'd post it anyway out of interest.

Obfuscated code:

let e x=
let rec f(s:string)=
let i=s.IndexOf(')')
if i>0 then
let j=s.LastIndexOf('(',i)
f(s.Substring(0,j)+f(s.Substring(j+1,i-j-1))+s.Substring(i+1))
else
let o=[|'+';'-';'*';'/'|]
let i=s.LastIndexOfAny(o)
let j=s.IndexOfAny(o,max(i-2)0,2)
let k=if j<0 then i else j
if k<0 then s else
let o=s.[k]
string((if o='+'then(+)else if o='-'then(-)else if o='*'then(*)else(/))(float(f(s.Substring(0,k))))(float(s.Substring(k+1))))
float(f x)

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Python

Number of characters: 382

Yet another Python solution, heavily using regular expression replacement. Each run through the loop the simplest expressions are computed and the results are put back into the string.

This is the unobfuscated code, unless you consider regular expressions to be obfuscated.

import re
from operator import *
operators = dict(zip("+-/*", (add, sub, truediv, mul)))
def compute(s):
def repl(m):
v1, op, v2 = m.groups()
return str(operators[op](float(v1), float(v2)))
while not re.match("^\d+\.\d+$", s):
s = re.sub("([.\d]+)\s*([+-/*])\s*([.\d]+)", repl, s)
s = re.sub("\(([.\d]+)\)", r"\1", s)
return s

Had this idea just as I was turning in and couldn't let it go until I wrote it down and made it work.

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Perl

Number of characters: 93

Fully obfuscated function: (93 characters if you join these three lines into one)

$_="(@ARGV)";s/\s//g;$n=qr/(-?\d+(\.\d+)?)/;
while(s.\($n\)|(?<=\()$n[-+*/]$n.eval$&.e){}
print

Clear/semi-obfuscated function:

$_="(@ARGV)";            # Set the default var to "(" argument ")"
s/\s//g;                 # Strip all spaces from $_
$n=qr/(-?\d+(\.\d+)?)/;  # Compile a regex for "number"


# repeatedly replace the sequence "(" NUM ")" with NUM, or if there aren't
# any of those, replace "(" NUM OP NUM with the result
# of doing an eval on just the NUM OP NUM bit.
while(s{\($n\)|(?<=\()$n[-+*/]$n}{eval$&}e){}


# print $_
print

I think this is pretty well explained in the "clear" version. The two main insights are that you can make the code uniform by surrounding the argument with parentheses at the start (special cases cost characters), and that it is sufficient, albeit massively inefficient, to only process stuff right next to an open parenthesis, replacing it with its result.

It's probably easiest to run this code as:

perl -le '$_="(@ARGV)";s/\s//g;$n=qr/(-?\d+(\.\d+)?)/;while(s.\($n\)|(?<=\()$n[-+*/]$n.eval$&.e){}print' '4 * (9 - 4) / (2 * 6 - 2) + 8'

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Fortran 77 (gfortran dialect, now with g77 support)

Number of characters: 2059

Obfuscated version:

      function e(c)
character*99 c
character b
real f(24)
integer i(24)
nf=0
ni=0
20   nf=kf(0.0,nf,f)
ni=ki(43,ni,i)
30   if (isp(c).eq.1) goto 20
h=fr(c)
31   g=fp(nf,f)
j=ip(ni,i)
select case(j)
case (40)
goto 20
case (42)
d=g*h
case (43)
d=g+h
case (45)
d=g-h
case (47)
d=g/h
end select
50   nf=kf(d,nf,f)
60   j=nop(c)
goto (20, 70, 75, 75, 60, 75, 60, 75) (j-39)
65   e=fp(nf,f)
return
70   h=fp(nf,f)
goto 31
75   ni=ki(j,ni,i)
goto 30
end
function kf(v,n,f)
real f(24)
kf=n+1
f(n+1)=v
return
end
function ki(j,n,i)
integer i(24)
ki=n+1
i(n+1)=j
return
end
function fp(n,f)
real f(24)
fp=f(n)
n=n-1
return
end
function ip(n,i)
integer i(24)
ip=i(n)
n=n-1
return
end
function nop(s)
character*99 s
l=1
do while(s(l:l).eq." ".and.l.lt.99)
l=l+1
enddo
nop=ichar(s(l:l))
s(l:l)=" "
return
end
function isp(s)
character*99 s
isp=0
l=1
do while(s(l:l).eq." ".and.l.lt.99)
l=l+1
enddo
isp=41-ichar(s(l:l))
if (isp.eq.1) s(l:l)=" "
return
end
function fr(s)
character*99 s
m=1
n=1
i=1
do while(i.le.99)
j=ichar(s(i:i))
if (j.eq.32) goto 90
if (j.ge.48.and.j.lt.58) goto 89
if (j.eq.43.or.j.eq.45) goto (89,80) m
if (j.eq.46) goto (83,80) n
80      exit
83      n=2
89      m=2
90      i=i+1
enddo
read(s(1:i-1),*) fr
do 91 j=1,i-1
s(j:j)=" "
91   continue
return
end

Clear version: (3340 characters with scaffold)

      program infixeval
character*99 c
do while (.true.)
do 10 i=1,99
c(i:i)=" "
10      continue
read(*,"(A99)") c
f=e(c)
write(*,*)f
enddo
end


function e(c)
character*99 c
character b
real f(24)                ! value stack
integer i(24)             ! operator stack
nf=0                      ! number of items on the value stack
ni=0                      ! number of items on the operator stack
20   nf=pushf(0.0,nf,f)
ni=pushi(43,ni,i)         ! ichar(+) = 43
D     write (*,*) "'",c,"'"
30   if (isp(c).eq.1) goto 20
h=fr(c)
D     write (*,*) "'",c,"'"
31   g=fpop(nf,f)
j=ipop(ni,i)
D     write(*,*) "Opperate ",g," ",char(j)," ",h
select case(j)
case (40)
goto 20
case (42)                 ! "*"
d=g*h
case (43)                 ! "+"
d=g+h
case (45)                 ! "-"
d=g-h
case (47)                 ! "*"
d=g/h
end select
50   nf=pushf(d,nf,f)
60   j=nop(c)
D     write(*,*) "Got op: ", char(j)
goto (20, 70, 75, 75, 60, 75, 60, 75) (j-39)
65   e=fpop(nf,f)
return
70   h=fpop(nf,f)              ! Encountered a "("
goto 31
75   ni=pushi(j,ni,i)
goto 30
end


c     push onto a real stack
c     OB as kf
function pushf(v,n,f)
real f(24)
pushf=n+1
f(n+1)=v
D     write(*,*) "Push ", v
return
end


c     push onto a integer stack
c     OB as ki
function pushi(j,n,i)
integer i(24)
pushi=n+1
i(n+1)=j
D     write(*,*) "Push ", char(j)
return
end


c     pop from real stack
c     OB as fp
function fpop(n,f)
real f(24)
fpop=f(n)
n=n-1
D      write (*,*) "Pop ", fpop
return
end


c     pop from integer stack
c     OB as ip
function ipop(n,i)
integer i(24)
ipop=i(n)
n=n-1
D      write (*,*) "Pop ", char(ipop)
return
end


c     Next OPerator: returns the next nonws character, and removes it
c     from the string
function nop(s)
character*99 s
l=1
do while(s(l:l).eq." ".and.l.lt.99)
l=l+1
enddo
nop=ichar(s(l:l))
s(l:l)=" "
return
end


c     IS an open Paren: return 1 if the next non-ws character is "("
c     (also overwrite it with a space. Otherwise return not 1
function isp(s)
character*99 s
isp=0
l=1
do while(s(l:l).eq." ".and.l.lt.99)
l=l+1
enddo
isp=41-ichar(s(l:l))
if (isp.eq.1) s(l:l)=" "
return
end


c     Float Read: return the next real number in the string and removes the
c     character
function fr(s)
character*99 s
m=1                      ! No sign (Minus or plus) so far
n=1                      ! No decimal so far
i=1
do while(i.le.99)
j=ichar(s(i:i))
if (j.eq.32) goto 90   ! skip spaces
if (j.ge.48.and.j.lt.58) goto 89
if (j.eq.43.or.j.eq.45) goto (89,80) m
if (j.eq.46) goto (83,80) n
c     not part of a number
80      exit
83      n=2
89      m=2
90      i=i+1
enddo
read(s(1:i-1),*) fr
do 91 j=1,i-1
s(j:j)=" "
91   continue
return
end

Notes This edited version is rather more evil than my first attempt. Same algorithm, but now inline with a horrible tangle of gotos. I've ditched the co-routines, but am now using a couple of flavors of computed branches. All error checking and reporting has been removed, but this version will silently recover from some classes of unexpected characters in the input. This version also compiles with g77.

The primary limits are still fortran's rigid formatting, long and ubiquitous keywords, and simple primitives.

小开

最佳答案

Perl (no eval)

Number of characters: ~~167~~ 106 (see below for the 106 character version)

Fully obfuscated function: (167 characters if you join these three lines into one)

sub e{my$_="($_[0])";s/\s//g;$n=q"(-?\d++(\.\d+)?+)";
@a=(sub{$1},1,sub{$3*$6},sub{$3+$6},4,sub{$3-$6},6,sub{$3/$6});
while(s:\($n\)|(?<=\()$n(.)$n:$a[7&ord$5]():e){}$_}

Clear/deobfuscated version:

sub e {
my $_ = "($_[0])";
s/\s//g;
$n=q"(-?\d++(\.\d+)?+)"; # a regex for "number", including capturing groups
# q"foo" in perl means the same as 'foo'
# Note the use of ++ and ?+ to tell perl
# "no backtracking"


@a=(sub{$1},             # 0 - no operator found
1,                   # placeholder
sub{$3*$6},          # 2 - ord('*') = 052
sub{$3+$6},          # 3 - ord('+') = 053
4,                   # placeholder
sub{$3-$6},          # 5 - ord('-') = 055
6,                   # placeholder
sub{$3/$6});         # 7 - ord('/') = 057


# The (?<=... bit means "find a NUM WHATEVER NUM sequence that happens
# immediately after a left paren", without including the left
# paren.  The while loop repeatedly replaces "(" NUM WHATEVER NUM with
# "(" RESULT and "(" NUM ")" with NUM.  The while loop keeps going
# so long as those replacements can be made.


while(s:\($n\)|(?<=\()$n(.)$n:$a[7&ord$5]():e){}


# A perl function returns the value of the last statement
$_
}

I had misread the rules initially, so I'd submitted a version with "eval". Here's a version without it.

The latest bit of insight came when I realized that the last octal digit in the character codes for +, -, /, and * is different, and that ord(undef) is 0. This lets me set up the dispatch table @a as an array, and just invoke the code at the location 7 & ord($3).

There's an obvious spot to shave off one more character - change q"" into '' - but that would make it harder to cut-and-paste into the shell.

Even shorter

Number of characters: ~~124~~ 106

Taking edits by ephemient into account, it's now down to 124 characters: (join the two lines into one)

sub e{$_=$_[0];s/\s//g;$n=q"(-?\d++(\.\d+)?+)";
1while s:\($n\)|$n(.)$n:($1,1,$3*$6,$3+$6,4,$3-$6,6,$6&&$3/$6)[7&ord$5]:e;$_}

Shorter still

Number of characters: ~~110~~ 106

The ruby solution down below is pushing me further, though I can't reach its 104 characters:

sub e{($_)=@_;$n='( *-?[.\d]++ *)';
s:\($n\)|$n(.)$n:(($1,$2-$4,$4&&$2/$4,$2*$4,$2+$4)x9)[.8*ord$3]:e?e($_):$_}

I had to give in and use ''. That ruby send trick is really useful for this problem.

Squeezing water from a stone

Number of characters: 106

A small contortion to avoid the divide-by-zero check.

sub e{($_)=@_;$n='( *-?[.\d]++ *)';
s:\($n\)|$n(.)$n:($1,0,$2*$4,$2+$4,0,$2-$4)[7&ord$3]//$2/$4:e?e($_):$_}

Here's the test harness for this function:

perl -le 'sub e{($_)=@_;$n='\''( *-?[.\d]++ *)'\'';s:\($n\)|$n(.)$n:($1,0,$2*$4,$2+$4,0,$2-$4)[7&ord$3]//$2/$4:e?e($_):$_}' -e 'print e($_) for @ARGV' '1 + 3' '1 + ((123 * 3 - 69) / 100)' '4 * (9 - 4) / (2 * 6 - 2) + 8' '2*3*4*5+99' '2.45/8.5*9.27+(5*0.0023) ' '1 + 3 / -8'

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Python

Number of characters: 235

Fully obfuscated function:

def g(a):
i=len(a)
while i:
try:m=g(a[i+1:]);n=g(a[:i]);a=str({'+':n+m,'-':n-m,'*':n*m,'/':n/(m or 1)}[a[i]])
except:i-=1;j=a.rfind('(')+1
if j:k=a.find(')',j);a=a[:j-1]+str(g(a[j:k]))+a[k+1:]
return float(a.replace('--',''))

Semi-obfuscated:

def g(a):
i=len(a);
# do the math
while i:
try:
# recursively evaluate left and right
m=g(a[i+1:])
n=g(a[:i])
# try to do the math assuming that a[i] is an operator
a=str({'+':n+m,'-':n-m,'*':n*m,'/':n/(m or 1)}[a[i]])
except:
# failure -> next try
i-=1
j=a.rfind('(')+1
# replace brackets in parallel (this part is executed first)
if j:
k=a.find(')',j)
a=a[:j-1]+str(g(a[j:k]))+a[k+1:]
return float(a.replace('--',''))

FWIW, the n+1th Python solution. In a blatant abuse of try-except I use a trial-and-error approach. It should handle all cases properly including stuff like -(8), --8 and g('-(1 - 3)'). It is re-entrant. Without support for the -- case which many implementations don't support, it is at 217 chars (see previous revision).

Thanks for an interesting hour on a Sunday and another 30 mins on Monday. Thanks to krubo for his nice dict.

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Ruby

Number of characters: 170

Obfuscated:

def s(x)
while x.sub!(/\(([^\(\)]*?)\)/){s($1)}
x.gsub!('--','')
end
while x.sub!(/(-?[\d.]+)[ ]*([+\-*\/])[ ]*(-?[\d.]+)/){$1.to_f.send($2,$3.to_f)}
end
x.strip.to_f
end

Readable:

def s(x)
while x.sub!(/\(([^\(\)]*?)\)/){s($1)}
x.gsub!('--','')
end
while x.sub!(/(-?[\d.]+)[ ]*([+\-*\/])[ ]*(-?[\d.]+)/){$1.to_f.send($2,$3.to_f)}
end
x.strip.to_f
end


[
['1 + 3 / -8', -0.5],
['2*3*4*5+99', 219],
['4 * (9 - 4) / (2 * 6 - 2) + 8', 10],
['1 + ((123 * 3 - 69) / 100)', 4],
['2.45/8.5*9.27+(5*0.0023)',2.68344117647059],
['(3+7) - (5+2)', 3]
].each do |pair|
a,b = s(String.new(pair[0])),pair[1]
print pair[0].ljust(25), ' = ', b, ' (', a==b, ')'
puts
end

There is no real obfuscation to this one, which I decided to post fresh since it's wildly different from my first. I should have seen this from the start. The process is a very simple process of elimination: find and resolve the highest pair of parenthesis (the most nested) into a number until no more are found, then resolve all the existing numbers and operations into the result. And, while resolving parenthetical statements I have it strip all double-dashes (Float.to_f doesn't know what to do with them).

So, it supports positive and negative numbers (+3, 3, & -3) and even negated sub-expressions within the parenthesis just by the order of processing. The only shorter implementation is the Perl (w/o eval) one.

Edit: I'm still chasing Perl, but this is the second smallest answer right now. I shrunk it with changes to the second regex and by changing the treatment of the string to be destructive (replaces the old string). This eliminated the need to duplicate the string, which I found out to just be a new pointer to the string. And renaming the function to s from solve saved a few characters.

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Python (without importing anything)

Number of characters: 222

I stole many tricks from Dave's answer, but I managed to shave off some more characters.

def e(s,l=0,n=0,f='+'):
if s:l=[c for c in s+')'if' '!=c]
while f!=')':
p=l.pop;m=p(0)
if m=='(':m=e(0,l)
while l[0]not in'+-*/)':m+=p(0)
m=float(m);n={'+':n+m,'-':n-m,'*':n*m,'/':n/(m or 1)}[f];f=p(0)
return n

Commented version:

def evaluate(stringexpr, listexpr=0, n=0, f_operation='+'):
# start out as taking 0 + the expression... (or could use 1 * ;)


# We'll prefer to keep the expression as a list of characters,
# so we can use .pop(0) to eat up the expression as we go.
if stringexpr:
listexpr = [c for c in stringexpr+')' if c!=' ']


# use ')' as sentinel to return the answer
while f_operation != ')':
m_next = listexpr.pop(0)
if m_next == '(':
# lists are passed by reference, so this call will eat the (parexp)
m_next = evaluate(None, listexpr)


else:
# rebuild any upcoming numeric chars into a string
while listexpr[0] not in '+-*/)':
m_next += listexpr.pop(0)


# Update n as the current answer.  But never divide by 0.
m = float(m_next)
n = {'+':n+m, '-':n-m, '*':n*m, '/':n/(m or 1)}[f_operation]


# prepare the next operation (known to be one of '+-*/)')
f_operation = listexpr.pop(0)


return n

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J

Number of characters: 208

After Jeff Moser's comment, I realized that I had completely forgotten about this language... I'm no expert, but my first attempt went rather well.

e=:>@{:@f@;:
f=:''&(4 :0)
'y x'=.x g y
while.($y)*-.')'={.>{.y do.'y x'=.(x,>(-.'/'={.>{.y){('%';y))g}.y end.y;x
)
g=:4 :0
z=.>{.y
if.z='('do.'y z'=.f}.y else.if.z='-'do.z=.'_',>{.}.y end.end.(}.y);":".x,z
)

It's a bit annoying, having to map x/y and -z into J's x%y and _z. Without that, maybe 50% of this code could disappear.

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Visual Basic.NET

Number of characters: 9759

I'm more of a bowler myself.

NOTE: does not take nested parentheses into account. Also, untested, but I'm pretty sure it works.

Imports Microsoft.VisualBasic
Imports System.Text
Imports System.Collections.Generic
Public Class Main
Public Shared Function DoArithmaticFunctionFromStringInput(ByVal MathematicalString As String) As Double
Dim numberList As New List(Of Number)
Dim operationsList As New List(Of IOperatable)
Dim currentNumber As New Number
Dim currentParentheticalStatement As New Parenthetical
Dim isInParentheticalMode As Boolean = False
Dim allCharactersInString() As Char = MathematicalString.ToCharArray
For Each mathChar In allCharactersInString
If mathChar = Number.ZERO_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.ONE_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.TWO_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.THREE_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.FOUR_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.FIVE_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.SIX_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.SEVEN_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.EIGHT_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.NINE_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Number.DECIMAL_POINT_STRING_REPRESENTATION Then
currentNumber.UpdateNumber(mathChar)
ElseIf mathChar = Addition.ADDITION_STRING_REPRESENTATION Then
Dim addition As New Addition


If Not isInParentheticalMode Then
operationsList.Add(addition)
numberList.Add(currentNumber)
Else
currentParentheticalStatement.AllNumbers.Add(currentNumber)
currentParentheticalStatement.AllOperators.Add(addition)
End If


currentNumber = New Number
ElseIf mathChar = Number.NEGATIVE_NUMBER_STRING_REPRESENTATION Then
If currentNumber.StringOfNumbers.Length > 0 Then
currentNumber.UpdateNumber(mathChar)


Dim subtraction As New Addition
If Not isInParentheticalMode Then
operationsList.Add(subtraction)
numberList.Add(currentNumber)
Else
currentParentheticalStatement.AllNumbers.Add(currentNumber)
currentParentheticalStatement.AllOperators.Add(subtraction)
End If


currentNumber = New Number
Else
currentNumber.UpdateNumber(mathChar)
End If
ElseIf mathChar = Multiplication.MULTIPLICATION_STRING_REPRESENTATION Then
Dim multiplication As New Multiplication


If Not isInParentheticalMode Then
operationsList.Add(multiplication)
numberList.Add(currentNumber)
Else
currentParentheticalStatement.AllNumbers.Add(currentNumber)
currentParentheticalStatement.AllOperators.Add(multiplication)
End If
currentNumber = New Number
ElseIf mathChar = Division.DIVISION_STRING_REPRESENTATION Then
Dim division As New Division


If Not isInParentheticalMode Then
operationsList.Add(division)
numberList.Add(currentNumber)
Else
currentParentheticalStatement.AllNumbers.Add(currentNumber)
currentParentheticalStatement.AllOperators.Add(division)
End If
currentNumber = New Number
ElseIf mathChar = Parenthetical.LEFT_PARENTHESIS_STRING_REPRESENTATION Then
isInParentheticalMode = True
ElseIf mathChar = Parenthetical.RIGHT_PARENTHESIS_STRING_REPRESENTATION Then
currentNumber = currentParentheticalStatement.EvaluateParentheticalStatement
numberList.Add(currentNumber)
isInParentheticalMode = False
End If
Next


Dim result As Double = 0
Dim operationIndex As Integer = 0
For Each numberOnWhichToPerformOperations As Number In numberList
result = operationsList(operationIndex).PerformOperation(result, numberOnWhichToPerformOperations)
operationIndex = operationIndex + 1
Next


Return result


End Function
Public Class Number
Public Const DECIMAL_POINT_STRING_REPRESENTATION As Char = "."
Public Const NEGATIVE_NUMBER_STRING_REPRESENTATION As Char = "-"
Public Const ZERO_STRING_REPRESENTATION As Char = "0"
Public Const ONE_STRING_REPRESENTATION As Char = "1"
Public Const TWO_STRING_REPRESENTATION As Char = "2"
Public Const THREE_STRING_REPRESENTATION As Char = "3"
Public Const FOUR_STRING_REPRESENTATION As Char = "4"
Public Const FIVE_STRING_REPRESENTATION As Char = "5"
Public Const SIX_STRING_REPRESENTATION As Char = "6"
Public Const SEVEN_STRING_REPRESENTATION As Char = "7"
Public Const EIGHT_STRING_REPRESENTATION As Char = "8"
Public Const NINE_STRING_REPRESENTATION As Char = "9"


Private _isNegative As Boolean
Public ReadOnly Property IsNegative() As Boolean
Get
Return _isNegative
End Get
End Property
Public ReadOnly Property ActualNumber() As Double
Get
Dim result As String = ""
If HasDecimal Then
If DecimalIndex = StringOfNumbers.Length - 1 Then
result = StringOfNumbers.ToString
Else
result = StringOfNumbers.Insert(DecimalIndex, DECIMAL_POINT_STRING_REPRESENTATION).ToString
End If
Else
result = StringOfNumbers.ToString
End If
If IsNegative Then
result = NEGATIVE_NUMBER_STRING_REPRESENTATION & result
End If
Return CType(result, Double)
End Get
End Property
Private _hasDecimal As Boolean
Public ReadOnly Property HasDecimal() As Boolean
Get
Return _hasDecimal
End Get
End Property
Private _decimalIndex As Integer
Public ReadOnly Property DecimalIndex() As Integer
Get
Return _decimalIndex
End Get
End Property
Private _stringOfNumbers As New StringBuilder
Public ReadOnly Property StringOfNumbers() As StringBuilder
Get
Return _stringOfNumbers
End Get
End Property
Public Sub UpdateNumber(ByVal theDigitToAppend As Char)
If IsNumeric(theDigitToAppend) Then
Me._stringOfNumbers.Append(theDigitToAppend)
ElseIf theDigitToAppend = DECIMAL_POINT_STRING_REPRESENTATION Then
Me._hasDecimal = True
Me._decimalIndex = Me._stringOfNumbers.Length
ElseIf theDigitToAppend = NEGATIVE_NUMBER_STRING_REPRESENTATION Then
Me._isNegative = Not Me._isNegative
End If
End Sub
Public Shared Function ConvertDoubleToNumber(ByVal numberThatIsADouble As Double) As Number
Dim numberResult As New Number
For Each character As Char In numberThatIsADouble.ToString.ToCharArray
numberResult.UpdateNumber(character)
Next
Return numberResult
End Function
End Class
Public MustInherit Class Operation
Protected _firstnumber As New Number
Protected _secondnumber As New Number
Public Property FirstNumber() As Number
Get
Return _firstnumber
End Get
Set(ByVal value As Number)
_firstnumber = value
End Set
End Property
Public Property SecondNumber() As Number
Get
Return _secondnumber
End Get
Set(ByVal value As Number)
_secondnumber = value
End Set
End Property
End Class
Public Interface IOperatable
Function PerformOperation(ByVal number1 As Double, ByVal number2 As Number) As Double
End Interface
Public Class Addition
Inherits Operation
Implements IOperatable
Public Const ADDITION_STRING_REPRESENTATION As String = "+"
Public Sub New()


End Sub
Public Function PerformOperation(ByVal number1 As Double, ByVal number2 As Number) As Double Implements IOperatable.PerformOperation
Dim result As Double = 0
result = number1 + number2.ActualNumber
Return result
End Function
End Class
Public Class Multiplication
Inherits Operation
Implements IOperatable
Public Const MULTIPLICATION_STRING_REPRESENTATION As String = "*"
Public Sub New()


End Sub
Public Function PerformOperation(ByVal number1 As Double, ByVal number2 As Number) As Double Implements IOperatable.PerformOperation
Dim result As Double = 0
result = number1 * number2.ActualNumber
Return result
End Function
End Class
Public Class Division
Inherits Operation
Implements IOperatable
Public Const DIVISION_STRING_REPRESENTATION As String = "/"
Public Const DIVIDE_BY_ZERO_ERROR_MESSAGE As String = "I took a lot of time to write this program. Please don't be a child and try to defile it by dividing by zero. Nobody thinks you are funny."
Public Sub New()


End Sub
Public Function PerformOperation(ByVal number1 As Double, ByVal number2 As Number) As Double Implements IOperatable.PerformOperation
If Not number2.ActualNumber = 0 Then
Dim result As Double = 0
result = number1 / number2.ActualNumber
Return result
Else
Dim divideByZeroException As New Exception(DIVIDE_BY_ZERO_ERROR_MESSAGE)
Throw divideByZeroException
End If
End Function
End Class
Public Class Parenthetical
Public Const LEFT_PARENTHESIS_STRING_REPRESENTATION As String = "("
Public Const RIGHT_PARENTHESIS_STRING_REPRESENTATION As String = ")"
Private _allNumbers As New List(Of Number)
Public Property AllNumbers() As List(Of Number)
Get
Return _allNumbers
End Get
Set(ByVal value As List(Of Number))
_allNumbers = value
End Set
End Property
Private _allOperators As New List(Of IOperatable)
Public Property AllOperators() As List(Of IOperatable)
Get
Return _allOperators
End Get
Set(ByVal value As List(Of IOperatable))
_allOperators = value
End Set
End Property
Public Sub New()


End Sub
Public Function EvaluateParentheticalStatement() As Number
Dim result As Double = 0
Dim operationIndex As Integer = 0
For Each numberOnWhichToPerformOperations As Number In AllNumbers
result = AllOperators(operationIndex).PerformOperation(result, numberOnWhichToPerformOperations)
operationIndex = operationIndex + 1
Next


Dim numberToReturn As New Number
numberToReturn = Number.ConvertDoubleToNumber(result)
Return numberToReturn
End Function
End Class
End Class

小开

Here comes another one:

Shell script (using sed+awk)

Number of characters: 295

obfuscated:

e(){ a="$1";while echo "$a"|grep -q \(;do eval "`echo "$a"|sed 's/\(.*\)(\([^()]*\))\(.*\)/a="\1\`e \"\2\"\`\3"/'`";done; echo "$a"|sed 's/\([-+*/]\) *\(-\?\) */ \1 \2/g'|awk '{t=$1;for(i=2;i<NF;i+=2){j=$(i+1);if($i=="+") t+=j; else if($i=="-") t-=j; else if($i=="*") t*=j; else t/=j}print t}';}

readable

e () {
a="$1"
# Recursively process bracket-expressions
while echo "$a"|grep -q \(; do
eval "`echo "$a"|
sed 's/\(.*\)(\([^()]*\))\(.*\)/a="\1\`e \"\2\"\`\3"/'`"
done
# Compute expression without brackets
echo "$a"|
sed 's/\([-+*/]\) *\(-\?\) */ \1 \2/g'|
awk '{
t=$1;
for(i=2;i<NF;i+=2){
j=$(i+1);
if($i=="+") t+=j;
else if($i=="-") t-=j;
else if($i=="*") t*=j;
else t/=j
}
print t
}'
}

Test:

str='  2.45 / 8.5  *  9.27   +    (   5   *  0.0023  ) '
echo "$str"|bc -l
e "$str"

Result:

2.68344117647058823526
2.68344

小开

Java

Number of Characters: 376

Updated version, now with more ? operator abuse!

Fully obfuscated solution:

static double e(String t){t="("+t+")";for(String s:new String[]{"+","-","*","/","(",")"})t=t.replace(s," "+s+" ");return f(new Scanner(t));}static double f(Scanner s){s.next();double a,v=s.hasNextDouble()?s.nextDouble():f(s);while(s.hasNext("[^)]")){char o=s.next().charAt(0);a=s.hasNextDouble()?s.nextDouble():f(s);v=o=='+'?v+a:o=='-'?v-a:o=='*'?v*a:v/a;}s.next();return v;}

Clear/semi-obfuscated function:

static double evaluate(String text) {
text = "(" + text + ")";
for (String s : new String[] {"+", "-", "*", "/", "(", ")" }) {
text = text.replace(s, " " + s + " ");
}
return innerEval(new Scanner(text));
}


static double innerEval(Scanner s) {
s.next();
double arg, val = s.hasNextDouble() ? s.nextDouble() : innerEval(s);
while (s.hasNext("[^)]")) {
char op = s.next().charAt(0);
arg = s.hasNextDouble() ? s.nextDouble() : innerEval(s);
val =
op == '+' ? val + arg :
op == '-' ? val - arg :
op == '*' ? val * arg :
val / arg;
}
s.next();
return val;
}

小开

I'm surprised nobody did it in Lex / Yacc or equivalent.

That would seem to yield the shortest source code that was also readable / maintainable.

小开

Ruby

Number of characters: ~~217~~ 179

~~This is the shortest ruby solution up to now (one heavily based on RegExp yields incorrect answers when string contains few groups of parenthesis)~~ -- no longer true. Solutions based on regex and substitution are shorter. This one is based on stack of accumulators and parses whole expression from left to right. It is re-entrant, and does not modify input string. It could be accused of breaking the rules of not using eval, as it calls Float's methods with identical names as their mathematical mnemonics (+,-,/,*).

Obfuscated code (old version, tweaked below):

def f(p);a,o=[0],['+']
p.sub(/-/,'+-').scan(/(?:(-?\d+(?:\.\d+)?)|(.))\s*/).each{|n|
q,w=n;case w;when'(';a<<0;o<<'+';when')';q=a.pop;else;o<<w
end if q.nil?;a[-1]=a[-1].method(o.pop).call(q.to_f) if !q.nil?};a[0];end

More obfuscated code:

def f(p);a,o=[0],[:+]
p.scan(/(?:(-?\d+(?:\.\d+)?)|(.))\s*/).each{|n|q,w=n;case w
when'(';a<<0;o<<:+;when')';q=a.pop;else;o<<w;end if !q
a<<a.pop.send(o.pop,q.to_f)if q};a[0];end

Clean code:

def f(p)
accumulators, operands = [0], ['+']
p.gsub(/-/,'+-').scan(/(?:(-?\d+(?:\.\d+)?)|(.))\s*/).each do |n|
number, operand = n
case operand
when '('
accumulators << 0
operands << '+'
when ')'
number = accumulators.pop
operands.pop
else
operands[-1] = operand
end if number.nil?
accumulators[-1] = accumulators.last.method(operands[-1]).call(number.to_f) unless number.nil?
end
accumulators.first
end

小开

MATLAB (v7.8.0)

Number of characters: 239

Obfuscated function:

function [v,s]=m(s),r=1;while s,s=regexp(s,'( ?)(?(1)-?)[\.\d]+|\S','match');c=s{end};s=[s{1:end-1}];if any(c>47),v=str2num(c);elseif c>41,[l,s]=m(s);v=[l/v l*v l+v l-v];v=v(c=='/*+-');if r,break;end;r=1;elseif c<41,break;end;r=r&c~=41;end

Clear(er) function:

function [value,str] = math(str)
returnNow = 1;
while str,
str = regexp(str,'( ?)(?(1)-?)[\.\d]+|\S','match');
current = str{end};
str = [str{1:end-1}];
if any(current > 47),
value = str2num(current);
elseif current > 41,
[leftValue,str] = math(str);
value = [leftValue/value leftValue*value ...
leftValue+value leftValue-value];
value = value(current == '/*+-');
if returnNow,
break;
end;
returnNow = 1;
elseif current < 41,
break;
end;
returnNow = returnNow & (c ~= 41);
end

Test:

>> [math('1 + 3 / -8'); ...
math('2*3*4*5+99'); ...
math('4 * (9 - 4) / (2 * 6 - 2) + 8'); ...
math('1 + ((123 * 3 - 69) / 100)'); ...
math('2.45/8.5*9.27+(5*0.0023)')]


ans =


-0.5000
219.0000
10.0000
4.0000
2.6834

Synopsis: A mixture of regular expressions and recursion. Pretty much the best I have been able to do so far, without cheating and using EVAL.

小开

Assembler

427 bytes

Obfuscated, assembled with the excellent A86 into a .com executable:

dd 0db9b1f89h, 081bee3h, 0e8af789h, 0d9080080h, 0bdac7674h, 013b40286h
dd 07400463ah, 0ccfe4508h, 08ce9f675h, 02fc8000h, 013b0057eh, 0feaac42ah
dd 0bedf75c9h, 0ba680081h, 04de801h, 04874f73bh, 04474103ch, 0e8e8b60fh
dd 08e8a003fh, 0e880290h, 0de0153h, 08b57e6ebh, 0d902a93eh, 046d891dh
dd 08906c783h, 05f02a93eh, 03cffcee8h, 057197510h, 02a93e8bh, 08b06ef83h
dd 05d9046dh, 02a93e89h, 03bc9d95fh, 0ac0174f7h, 074f73bc3h, 0f3cac24h
dd 0eed9c474h, 0197f0b3ch, 07cc4940fh, 074f73b09h, 0103cac09h, 0a3ce274h
dd 0e40a537eh, 0e0d90274h, 02a3bac3h, 021cd09b4h, 03e8b20cdh, 0ff8102a9h
dd 0ed7502abh, 0474103ch, 0e57d0b3ch, 0be02a3bfh, 014d903a3h, 0800344f6h
dd 02db00574h, 0d9e0d9aah, 0d9029f2eh, 0bb34dfc0h, 08a0009h, 01c75f0a8h
dd 020750fa8h, 0b0f3794bh, 021e9aa30h, 0de607400h, 08802990eh, 0de07df07h
dd 0c392ebc1h, 0e8c0008ah, 0aa300404h, 0f24008ah, 04baa3004h, 02eb0ee79h
dd 03005c6aah, 0c0d90ab1h, 0e9defcd9h, 02a116deh, 0e480e0dfh, 040fc8045h
dd 0ede1274h, 0c0d90299h, 015dffcd9h, 047300580h, 0de75c9feh, 0303d804fh
dd 03d80fa74h, 04f01752eh, 0240145c6h, 0dfff52e9h, 0d9029906h, 0f73b025fh
dd 03caca174h, 07fed740ah, 0df07889ah, 0277d807h, 047d9c1deh, 0990ede02h
dd 025fd902h, 03130e0ebh, 035343332h, 039383736h, 02f2b2d2eh, 02029282ah
dd 0e9000a09h, 07fc9f9c1h, 04500000fh, 0726f7272h
db 024h, 0abh, 02h

EDIT: Unobfuscated source:

        mov [bx],bx
finit
mov si,81h
mov di,si
mov cl,[80h]
or cl,bl
jz ret
l1:
lodsb
mov bp,d1
mov ah,19
l2:
cmp al,[bp]
je l3
inc bp
dec ah
jne l2
jmp exit
l3:
cmp ah,2
jle l4
mov al,19
sub al,ah
stosb
l4:
dec cl
jnz l1
mov si,81h
push done


decode:
l5:
call l7
l50:
cmp si,di
je ret
cmp al,16
je ret
db 0fh, 0b6h, 0e8h ; movzx bp,al
call l7
mov cl,[bp+op-11]
mov byte ptr [sm1],cl
db 0deh
sm1:db ?
jmp l50


open:
push di
mov di,word ptr [s]
fstp dword ptr [di]
mov [di+4],bp
add di,6
mov word ptr [s],di
pop di
call decode
cmp al,16
jne ret
push di
mov di,word ptr [s]
sub di,6
mov bp,[di+4]
fld dword ptr [di]
mov word ptr [s],di
pop di
fxch st(1)
cmp si,di
je ret
lodsb
ret






l7: cmp si,di
je exit
lodsb
cmp al,15
je open
fldz
cmp al,11
jg exit
db 0fh, 94h, 0c4h ; sete ah
jl l10
l9:
cmp si,di
je l12
lodsb
cmp al,16
je ret
l10:
cmp al,10
jle l12i


l12:
or ah,ah
je l13
fchs
l13:
ret


exit:
mov dx,offset res
mov ah,9
int 21h
int 20h


done:
mov di,word ptr [s]
cmp di,(offset s)+2
jne exit
cmp al,16
je ok
cmp al,11
jge exit
ok:
mov di,res
mov si,res+100h
fst dword ptr [si]
test byte ptr [si+3],80h
jz pos
mov al,'-'
stosb
fchs
pos:
fldcw word ptr [cw]
fld st(0)
fbstp [si]
mov bx,9
l1000:
mov al,[si+bx]
test al,0f0h
jne startu
test al,0fh
jne startl
dec bx
jns l1000
mov al,'0'
stosb
jmp frac


l12i:
je l11
fimul word ptr [d3]
mov [bx],al
fild word ptr [bx]
faddp
jmp l9
ret


startu:
mov al,[si+bx]
shr al,4
add al,'0'
stosb
startl:
mov al,[si+bx]
and al,0fh
add al,'0'
stosb
dec bx
jns startu


frac:
mov al,'.'
stosb
mov byte ptr [di],'0'
mov cl,10
fld st(0)
frndint
frac1:
fsubp st(1)
ficom word ptr [zero]
fstsw ax
and ah,045h
cmp ah,040h
je finished
fimul word ptr [d3]
fld st(0)
frndint
fist word ptr [di]
add byte ptr [di],'0'
inc di
dec cl
jnz frac1


finished:
dec di
cmp byte ptr [di],'0'
je finished
cmp byte ptr [di],'.'
jne f2
dec di
f2:
mov byte ptr [di+1],'$'
exit2:
jmp exit




l11:
fild word ptr [d3]
fstp dword ptr [bx+2]
l111:
cmp si,di
je ret
lodsb
cmp al,10
je exit2
jg ret
mov [bx],al
fild word ptr [bx]
fdiv dword ptr [bx+2]
faddp
fld dword ptr [bx+2]
fimul word ptr [d3]
fstp dword ptr [bx+2]
jmp l111




d1: db '0123456789.-+/*()', 32, 9
d3: dw 10
op: db 0e9h, 0c1h, 0f9h, 0c9h
cw: dw 0f7fh
zero: dw 0
res:db 'Error$'
s:  dw (offset s)+2

小开

SNOBOL4

Number of characters: 232

        a = pos(0) | '('
n = span('0123456789.')
j = '!+;!-;!*;!/;       output = e'
d       j '!' len(1) . y = "    e a . q n . l '" y "' n . r = q (l " y " r)     :s(p)"  :s(d)
k = code(j)
e = input
s       e ' ' = :s(s)
p       e ('(' n . i ')') = i   :s(p)f<k>
end

This is a semi-cheat. It uses code() (a variant of eval) to de-compress itself, but not to evaluate the input expression.

De-obfuscated version, without code:

        prefix = pos(0) | '('
num = span('0123456789.')
expr = input
spaces  expr ' ' = ''   :s(spaces)
paren   expr ('(' num . x ')') = x      :s(paren)
add     expr (prefix . pfx) (num . l) '+' (num . r) = pfx (l + r)       :s(paren)
sub     expr (prefix . pfx) (num . l) '-' (num . r) = pfx (l - r)       :s(paren)
mul     expr (prefix . pfx) (num . l) '*' (num . r) = pfx (l * r)       :s(paren)
div     expr (prefix . pfx) (num . l) '/' (num . r) = pfx (l / r)       :s(paren)
output = expr
end

Strategy:

First, remove all spaces (spaces)
Whenever possible, remove parentheses surrounding a number (paren)
Otherwise, find a simple expression involving two numbers, prefixed by '(' or at the start of the string
If none of the above rules apply, the expression is fully evaluated. Now if the input was well formed we should be left with a number.

Example:

1 + (2 * 3) + 4
1+(2*3)+4 [spaces]
1+(6)+4 [mul]
1+6+4 [paren]
7+4 [add]
11 [add]

小开

Ruby

Number of characters: 103

N='( *-?[\d.]+ *)'
def e x
x.sub!(/\(#{N}\)|#{N}([^.\d])#{N}/){$1or(e$2).send$3,e($4)}?e(x):x.to_f
end

This is a ~~non-recursive~~ version of The Wicked Flea's solution. Parenthesized sub-expressions are evaluated bottom-up instead of top-down.

Edit: Converting the 'while' to a conditional + tail recursion has saved a few characters, so it is no longer non-recursive (though the recursion is not semantically necessary.)

Edit: Borrowing Daniel Martin's idea of merging the regexps saves another 11 characters!

Edit: That recursion is even more useful than I first thought! x.to_f can be rewritten as e(x), if x happens to contain a single number.

Edit: Using 'or' instead of '||' allows a pair of parentheses to be dropped.

Long version:

# Decimal number, as a capturing group, for substitution
# in the main regexp below.
N='( *-?[\d.]+ *)'


# The evaluation function
def e(x)
matched = x.sub!(/\(#{N}\)|#{N}([^\d.])#{N}/) do
# Group 1 is a numeric literal in parentheses.  If this is present then
# just return it.
if $1
$1
# Otherwise, $3 is an operator symbol and $2 and $4 are the operands
else
# Recursively call e to parse the operands (we already know from the
# regexp that they are numeric literals, and this is slightly shorter
# than using :to_f)
e($2).send($3, e($4))
# We could have converted $3 to a symbol ($3.to_s) or converted the
# result back to string form, but both are done automatically anyway
end
end
if matched then
# We did one reduction. Now recurse back and look for more.
e(x)
else
# If the string doesn't look like a non-trivial expression, assume it is a
# string representation of a real number and attempt to parse it
x.to_f
end
end

小开

C++

Chars: 1670

 // not trying to be terse here
#define DIGIT(c)((c)>='0' && (c) <= '9')
#define WHITE(pc) while(*pc == ' ') pc++
#define LP '('
#define RP ')'


bool SeeNum(const char* &pc, float& fNum){
WHITE(pc);
if (!(DIGIT(*pc) || (*pc=='.'&& DIGIT(pc[1])))) return false;
const char* pc0 = pc;
while(DIGIT(*pc)) pc++;
if (*pc == '.'){
pc++;
while(DIGIT(*pc)) pc++;
}
char buf[200];
int len = pc - pc0;
strncpy(buf, pc0, len); buf[len] = 0;
fNum = atof(buf);
return true;
}


bool SeeChar(const char* &pc, char c){
WHITE(pc);
if (*pc != c) return false;
pc++;
return true;
}


void ParsExpr(const char* &pc, float &fNum);


void ParsPrim(const char* &pc, float &fNum){
if (SeeNum(pc, fNum));
else if (SeeChar(pc, LP)){
ParsExpr(pc, fNum);
if (!SeeChar(pc, RP)) exit(0);
}
else exit(0); // you can abort better than this
}


void ParsUnary(const char* &pc, float &fNum){
if (SeeChar(pc, '-')){
pc+;
ParsUnary(pc, fNum);
fNum = -fNum;
}
else {
ParsPrim(pc, fNum);
}
}


void ParsExpr(const char* &pc, float &fNum){
ParsUnary(pc, fNum);
float f1 = 0;
while(true){
if (SeeChar(pc, '+')){
ParsUnary(pc, f1);
fNum += f1;
}
else if (SeeChar(pc, '-')){
ParsUnary(pc, f1);
fNum -= f1;
}
else if (SeeChar(pc, '*')){
ParsUnary(pc, f1);
fNum *= f1;
}
else if (SeeChar(pc, '/')){
ParsUnary(pc, f1);
fNum /= f1;
}
else break;
}
}

This is just LL1 (recursive descent). I like to do it this way (although I use doubles) because it's plenty fast, and easy to insert routines to handle precedence levels.

小开

C#

Number of Characters: 355

I took Noldorin's Answer and modified it, so give Noldorin 99% of the credit for this. Best I could do with the algorithm was using was 408 characters. See Noldorin's Answer for the clearer code version.

Changes made:
Change char comparisons to compare against numbers.
Removed some default declarations and combined same type of declarations.
Re-worked some of the if statments.

float q(string x){float v,n;if(!float.TryParse(x,out v)){x+=';';int t=0,l=0,i=0;char o,s='?',p='+';for(;i<x.Length;i++){o=s;if(x[i]!=32){s=x[i];if(char.IsDigit(x[i])|s==46|(s==45&o!=49))s='1';if(s==41)l--;if(s!=o&l==0){if(o==49|o==41){n=q(x.Substring(t,i-t));v=p==43?v+n:p==45?v-n:p==42?v*n:p==47?v/n:v;p=x[i];}t=i;if(s==40)t++;}if(s==40)l++;}}}return v;}

Edit: knocked it down some more, from 361 to 355, by removing one of the return statments.

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C# with Regex

Number of characters: 294

This is partially based off Jeff Moser's answer, but with a significantly simplified evaluation technique. There might even be further ways to reduce the char count, but I'm quite pleased now that there's a C# solution under 300 chars!

Fully obfuscated code:

float e(string x){while(x.Contains("("))x=Regex.Replace(x,@"\(([^\(]*?)\)",m=>e(m.Groups[1].Value).ToString());float r=0;foreach(Match m in Regex.Matches("+"+x,@"\D ?-?[\d.]+")){var o=m.Value[0];var v=float.Parse(m.Value.Substring(1));r=o=='+'?r+v:o=='-'?r-v:o=='*'?r*v:r/v;}return r;}

Clearer code:

float e(string x)
{
while (x.Contains("("))
x = Regex.Replace(x, @"\(([^\(]*?)\)", m => e(m.Groups[1].Value).ToString());
float r = 0;
foreach (Match m in Regex.Matches("+" + x, @"\D ?-?[\d.]+"))
{
var o = m.Value[0];
var v = float.Parse(m.Value.Substring(1));
r = o == '+' ? r + v : o == '-' ? r - v : o == '*' ? r * v : r / v;
}
return r;
}

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C (VS2005)

Number of Characters: 1360

Abuse of preprocessor and warnings for fun code layout (scroll down to see):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define b main
#define c(a) b(a,0)
#define d -1
#define e -2
#define g break
#define h case
#define hh h
#define hhh h
#define w(i) case i
#define i return
#define j switch
#define k float
#define l realloc
#define m sscanf
#define n int _
#define o char
#define t(u) #u
#define q(r) "%f" t(r)  "n"
#define s while
#define v default
#define ex exit
#define W printf
#define x fn()
#define y strcat
#define z strcpy
#define Z strlen


char*p    =0    ;k    *b    (n,o**    a){k*f
;j(_){    hh   e:     i*    p==40?    (++p,c
(d        ))  :(      f=        l(        0,
4)        ,m (p       ,q        (%        ),
f,&_),    p+=_        ,f       );        hh
d:f=c(    e);s        (1      ){        j(
*p    ++ ){       hh     0:        hh
41    :i  f;      hh    43        :*
f+=*c(    e)   ;g     ;h    45:*f=    *f-*c(
e);g;h    42    :*    f=    *f**c(    e);g;h


47:*f      /=*c      (e);     g;   v:    c(0);}
}w(1):    if(p&&    printf    (q  ((     "\\"))
,*  c(    d)  ))    g;  hh    0: ex      (W
(x  ))    ;v  :p    =(        p?y:       z)(l(p
,Z(1[     a]  )+    (p        ?Z(p           )+
1:1))     ,1  [a    ])  ;b    (_ -1          ,a
+1  );    g;  }i    0;};fn    ()  {n     =42,p=
43  ;i     "Er"      "ro"     t(   r)    "\n";}

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PowerBASIC

Number of characters: ~400

A bit ugly, but it works. :) I'm sure regexp would have made it even smaller.

DEFDBL E,f,i,z,q,a,v,o
DEFSTR s,c,k,p


FUNCTION E(s)


i=LEN(s)
DO
IF MID$(s,i,1)="("THEN
q=INSTR(i,s,")")
s=LEFT$(s,i-1)+STR$(E(MID$(s,i+1,q-i-1)))+MID$(s,q+1)
END IF
i-=1
LOOP UNTIL i=0


k="+-*/"
DIM p(PARSECOUNT(s,ANY k))
PARSE s,p(),ANY k


a=VAL(p(0))


FOR i=1TO LEN(s)
c=MID$(s,i,1)
q=INSTR(k,c)
IF q THEN
z+=1
IF o=0 THEN o=q ELSE p(z)=c+p(z)
IF TRIM$(p(z))<>"" THEN
v=VAL(p(z))
a=CHOOSE(o,a+v,a-v,a*v,a/v)
o=0
END IF
END IF
NEXT


E=a
END FUNCTION

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C#, 264 characters

Strategy: the first 2 lines get rid of parentheses by induction. Then I split by \-?[\d.]+ to get numbers and operators. then using aggregate to reduce the string array to a double value.

Variable explanations

m is parenthesized expression with no nested parentheses.
d is a placeholder for that awkward TryParse syntax.
v is the accumulator for the final value
t is the current token.

float E(string s){var d=999f;while(d-->1)s=Regex.Replace(s,@"(([^(]?))",m=>E(m.Groups[1].Value)+"");return Regex.Split(s,@"(-?[\d.]+)").Aggregate(d,(v,t)=>(t=t.Trim()).Length==0?v:!float.TryParse(t,out d)?(s=t)==""?0:v:s=="/"?v/d:s=="-"?v-d:s==""?v*d:v+d);}

    float F(string s) {
var d=999f;
while(d-->1)
s=Regex.Replace(s,@"\(([^\(]*?)\)",m=>F(m.Groups[1].Value)+"");
return Regex.Split(s, @"(\-?[\d\.]+)")
.Aggregate(d, (v, t) =>
(t=t.Trim()).Length == 0 ? v :
!float.TryParse(t, out d) ? (s=t) == "" ? 0 : v :
s == "/" ? v / d :
s == "-" ? v - d :
s == "*" ? v * d :
v + d);
}

EDIT: shamelessly stole parts from noldorin's answer, reused s as the operator variable.

EDIT: 999 nested parentheses should be enough for anyone.

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SQL (SQL Server 2008)

Number of characters: 4202

Fully obfuscated function:

WITH Input(id,str)AS(SELECT 1,'1 + 3 / -8'UNION ALL SELECT 2,'2*3*4*5+99'UNION ALL SELECT 3,'4 * (9 - 4)/ (2 * 6 - 2)+ 8'UNION ALL SELECT 4,'1 + ((123 * 3 - 69)/ 100)'UNION ALL SELECT 5,'2.45/8.5*9.27+(5*0.0023)'),Separators(i,ch,str_src,priority)AS(SELECT 1,'-',1,1UNION ALL SELECT 2,'+',1,1UNION ALL SELECT 3,'*',1,1UNION ALL SELECT 4,'/',1,1UNION ALL SELECT 5,'(',0,0UNION ALL SELECT 6,')',0,0),SeparatorsStrSrc(str,i)AS(SELECT CAST('['AS varchar(max)),0UNION ALL SELECT str+ch,SSS.i+1FROM SeparatorsStrSrc SSS INNER JOIN Separators S ON SSS.i=S.i-1WHERE str_src<>0),SeparatorsStr(str)AS(SELECT str+']'FROM SeparatorsStrSrc WHERE i=(SELECT COUNT(*)FROM Separators WHERE str_src<>0)),ExprElementsSrc(id,i,tmp,ele,pre_ch,input_str)AS(SELECT id,1,CAST(LEFT(str,1)AS varchar(max)),CAST(''AS varchar(max)),CAST(' 'AS char(1)),SUBSTRING(str,2,LEN(str))FROM Input UNION ALL SELECT id,CASE ele WHEN''THEN i ELSE i+1 END,CAST(CASE WHEN LEFT(input_str,1)=' 'THEN''WHEN tmp='-'THEN CASE WHEN pre_ch LIKE(SELECT str FROM SeparatorsStr)THEN tmp+LEFT(input_str,1)ELSE LEFT(input_str,1)END WHEN LEFT(input_str,1)IN(SELECT ch FROM Separators)OR tmp IN(SELECT ch FROM Separators)THEN LEFT(input_str,1)ELSE tmp+LEFT(input_str,1)END AS varchar(max)),CAST(CASE WHEN LEFT(input_str,1)=' 'THEN tmp WHEN LEFT(input_str,1)='-'THEN CASE WHEN tmp IN(SELECT ch FROM Separators)THEN tmp ELSE''END WHEN LEFT(input_str,1)IN(SELECT ch FROM Separators)OR tmp IN(SELECT ch FROM Separators)THEN CASE WHEN tmp='-'AND pre_ch LIKE(SELECT str FROM SeparatorsStr)THEN''ELSE tmp END ELSE''END AS varchar(max)),CAST(LEFT(ele,1)AS char(1)),SUBSTRING(input_str,2,LEN(input_str))FROM ExprElementsSrc WHERE input_str<>''OR tmp<>''),ExprElements(id,i,ele)AS(SELECT id,i,ele FROM ExprElementsSrc WHERE ele<>''),Scanner(id,i,val)AS(SELECT id,i,CAST(ele AS varchar(max))FROM ExprElements WHERE ele<>''UNION ALL SELECT id,MAX(i)+1,NULL FROM ExprElements GROUP BY id),Operator(op,priority)AS(SELECT ch,priority FROM Separators WHERE priority<>0),Calc(id,c,i,pop_count,s0,s1,s2,stack,status)AS(SELECT Scanner.id,1,1,0,CAST(scanner.val AS varchar(max)),CAST(NULL AS varchar(max)),CAST(NULL AS varchar(max)),CAST(''AS varchar(max)),CAST('init'AS varchar(max))FROM Scanner WHERE Scanner.i=1UNION ALL SELECT Calc.id,Calc.c+1,Calc.i,3,NULL,NULL,NULL,CASE Calc.s1 WHEN'+'THEN CAST(CAST(Calc.s2 AS real)+CAST(Calc.s0 AS real)AS varchar(max))WHEN'-'THEN CAST(CAST(Calc.s2 AS real)-CAST(Calc.s0 AS real)AS varchar(max))WHEN'*'THEN CAST(CAST(Calc.s2 AS real)*CAST(Calc.s0 AS real)AS varchar(max))WHEN'/'THEN CAST(CAST(Calc.s2 AS real)/CAST(Calc.s0 AS real)AS varchar(max))ELSE NULL END+' '+stack,CAST('calc '+Calc.s1 AS varchar(max))FROM Calc INNER JOIN Scanner NextVal ON Calc.id=NextVal.id AND Calc.i+1=NextVal.i WHERE Calc.pop_count=0AND ISNUMERIC(Calc.s2)=1AND Calc.s1 IN(SELECT op FROM Operator)AND ISNUMERIC(Calc.s0)=1AND(SELECT priority FROM Operator WHERE op=Calc.s1)>=COALESCE((SELECT priority FROM Operator WHERE op=NextVal.val),0)UNION ALL SELECT Calc.id,Calc.c+1,Calc.i,3,NULL,NULL,NULL,s1+' '+stack,CAST('paren'AS varchar(max))FROM Calc WHERE pop_count=0AND s2='('AND ISNUMERIC(s1)=1AND s0=')'UNION ALL SELECT Calc.id,Calc.c+1,Calc.i,Calc.pop_count-1,s1,s2,CASE WHEN LEN(stack)>0THEN SUBSTRING(stack,1,CHARINDEX(' ',stack)-1)ELSE NULL END,CASE WHEN LEN(stack)>0THEN SUBSTRING(stack,CHARINDEX(' ',stack)+1,LEN(stack))ELSE''END,CAST('pop'AS varchar(max))FROM Calc WHERE Calc.pop_count>0UNION ALL SELECT Calc.id,Calc.c+1,Calc.i+1,Calc.pop_count,CAST(NextVal.val AS varchar(max)),s0,s1,coalesce(s2,'')+' '+stack,cast('read'as varchar(max))FROM Calc INNER JOIN Scanner NextVal ON Calc.id=NextVal.id AND Calc.i+1=NextVal.i WHERE NextVal.val IS NOT NULL AND Calc.pop_count=0AND((Calc.s0 IS NULL OR calc.s1 IS NULL OR calc.s2 IS NULL)OR NOT(ISNUMERIC(Calc.s2)=1AND Calc.s1 IN(SELECT op FROM Operator)AND ISNUMERIC(calc.s0)=1AND (SELECT priority FROM Operator WHERE op=Calc.s1)>=COALESCE((SELECT priority FROM Operator WHERE op=NextVal.val),0))AND NOT(s2='('AND ISNUMERIC(s1)=1AND s
0=')')))SELECT Calc.id,Input.str,Calc.s0 AS result FROM Calc INNER JOIN Input ON Calc.id=Input.id WHERE Calc.c=(SELECT MAX(c)FROM Calc calc2 WHERE Calc.id=Calc2.id)ORDER BY id

Clear/semi-obfuscated function:

WITH
Input(id, str) AS (
SELECT 1, '1 + 3 / -8'
UNION ALL SELECT 2, '2*3*4*5+99'
UNION ALL SELECT 3, '4 * (9 - 4) / (2 * 6 - 2) + 8'
UNION ALL SELECT 4, '1 + ((123 * 3 - 69) / 100)'
UNION ALL SELECT 5, '2.45/8.5*9.27+(5*0.0023)'
)
, Separators(i, ch, str_src, priority) AS (
SELECT 1, '-', 1, 1
UNION ALL SELECT 2, '+', 1, 1
UNION ALL SELECT 3, '*', 1, 1
UNION ALL SELECT 4, '/', 1, 1
UNION ALL SELECT 5, '(', 0, 0
UNION ALL SELECT 6, ')', 0, 0
)
, SeparatorsStrSrc(str, i) AS (
SELECT CAST('[' AS varchar(max)), 0
UNION ALL
SELECT
str + ch
, SSS.i + 1
FROM
SeparatorsStrSrc SSS
INNER JOIN Separators S ON SSS.i = S.i - 1
WHERE
str_src <> 0
)
, SeparatorsStr(str) AS (
SELECT str + ']' FROM SeparatorsStrSrc
WHERE i = (SELECT COUNT(*) FROM Separators WHERE str_src <> 0)
)
, ExprElementsSrc(id, i, tmp, ele, pre_ch, input_str) AS (
SELECT
id
, 1
, CAST(LEFT(str, 1) AS varchar(max))
, CAST('' AS varchar(max))
, CAST(' ' AS char(1))
, SUBSTRING(str, 2, LEN(str))
FROM
Input
UNION ALL
SELECT
id
, CASE ele
WHEN '' THEN i
ELSE i + 1
END
, CAST(
CASE
WHEN LEFT(input_str, 1) = ' '
THEN ''
WHEN tmp = '-'
THEN CASE
WHEN pre_ch LIKE (SELECT str FROM SeparatorsStr)
THEN tmp + LEFT(input_str, 1)
ELSE LEFT(input_str, 1)
END
WHEN LEFT(input_str, 1) IN (SELECT ch FROM Separators)
OR
tmp IN (SELECT ch FROM Separators)
THEN LEFT(input_str, 1)
ELSE tmp + LEFT(input_str, 1)
END
AS varchar(max))
, CAST(
CASE
WHEN LEFT(input_str, 1) = ' '
THEN tmp
WHEN LEFT(input_str, 1) = '-'
THEN CASE
WHEN tmp IN (SELECT ch FROM Separators)
THEN tmp
ELSE ''
END
WHEN LEFT(input_str, 1) IN (SELECT ch FROM Separators)
OR
tmp IN (SELECT ch FROM Separators)
THEN CASE
WHEN tmp = '-' AND pre_ch LIKE (SELECT str FROM SeparatorsStr)
THEN ''
ELSE tmp
END
ELSE ''
END
AS varchar(max))
, CAST(LEFT(ele, 1) AS char(1))
, SUBSTRING(input_str, 2, LEN(input_str))
FROM
ExprElementsSrc
WHERE
input_str <> ''
OR
tmp <> ''
)
, ExprElements(id, i, ele) AS (
SELECT
id
, i
, ele
FROM
ExprElementsSrc
WHERE
ele <> ''
)
, Scanner(id, i, val) AS (
SELECT
id
, i
, CAST(ele AS varchar(max))
FROM
ExprElements
WHERE
ele <> ''
UNION ALL
SELECT
id
, MAX(i) + 1
, NULL
FROM
ExprElements
GROUP BY
id
)
, Operator(op, priority) AS (
SELECT
ch
, priority
FROM
Separators
WHERE
priority <> 0
)
, Calc(id, c, i, pop_count, s0, s1, s2, stack, status) AS (
SELECT
Scanner.id
, 1
, 1
, 0
, CAST(scanner.val AS varchar(max))
, CAST(NULL AS varchar(max))
, CAST(NULL AS varchar(max))
, CAST('' AS varchar(max))
, CAST('init' AS varchar(max))
FROM
Scanner
WHERE
Scanner.i = 1
UNION ALL
SELECT
Calc.id
, Calc.c + 1
, Calc.i
, 3
, NULL
, NULL
, NULL
, CASE Calc.s1
WHEN '+' THEN CAST(CAST(Calc.s2 AS real) + CAST(Calc.s0 AS real) AS varchar(max))
WHEN '-' THEN CAST(CAST(Calc.s2 AS real) - CAST(Calc.s0 AS real) AS varchar(max))
WHEN '*' THEN CAST(CAST(Calc.s2 AS real) * CAST(Calc.s0 AS real) AS varchar(max))
WHEN '/' THEN CAST(CAST(Calc.s2 AS real) / CAST(Calc.s0 AS real) AS varchar(max))
ELSE NULL
END
+ ' '
+ stack
, CAST('calc ' + Calc.s1 AS varchar(max))
FROM
Calc
INNER JOIN Scanner NextVal ON Calc.id = NextVal.id
AND Calc.i + 1 = NextVal.i
WHERE
Calc.pop_count = 0
AND ISNUMERIC(Calc.s2) = 1
AND Calc.s1 IN (SELECT op FROM Operator)
AND ISNUMERIC(Calc.s0) = 1
AND (SELECT priority FROM Operator WHERE op = Calc.s1)
>= COALESCE((SELECT priority FROM Operator WHERE op = NextVal.val), 0)
UNION ALL
SELECT
Calc.id
, Calc.c + 1
, Calc.i
, 3
, NULL
, NULL
, NULL
, s1 + ' ' + stack
, CAST('paren' AS varchar(max))
FROM
Calc
WHERE
pop_count = 0
AND s2 = '('
AND ISNUMERIC(s1) = 1
AND s0 = ')'
UNION ALL
SELECT
Calc.id
, Calc.c + 1
, Calc.i
, Calc.pop_count - 1
, s1
, s2
, CASE
WHEN LEN(stack) > 0
THEN SUBSTRING(stack, 1, CHARINDEX(' ', stack) - 1)
ELSE NULL
END
, CASE
WHEN LEN(stack) > 0
THEN SUBSTRING(stack, CHARINDEX(' ', stack) + 1, LEN(stack))
ELSE ''
END
, CAST('pop' AS varchar(max))
FROM
Calc
WHERE
Calc.pop_count > 0
UNION ALL
SELECT
Calc.id
, Calc.c + 1
, Calc.i + 1
, Calc.pop_count
, CAST(NextVal.val AS varchar(max))
, s0
, s1
, coalesce(s2, '') + ' ' + stack
, cast('read' as varchar(max))
FROM
Calc
INNER JOIN Scanner NextVal ON Calc.id = NextVal.id
AND Calc.i + 1 = NextVal.i
WHERE
NextVal.val IS NOT NULL
AND Calc.pop_count = 0
AND (
(Calc.s0 IS NULL or calc.s1 is null or calc.s2 is null)
OR
NOT(
ISNUMERIC(Calc.s2) = 1
AND Calc.s1 IN (SELECT op FROM Operator)
AND ISNUMERIC(calc.s0) = 1
AND (SELECT priority FROM Operator WHERE op = Calc.s1)
>= COALESCE((SELECT priority FROM Operator WHERE op = NextVal.val), 0)
)
AND NOT(s2 = '(' AND ISNUMERIC(s1) = 1 AND s0 = ')')
)
)
SELECT
Calc.id
, Input.str
, Calc.s0 AS result
FROM
Calc
INNER JOIN Input ON Calc.id = Input.id
WHERE
Calc.c = (SELECT MAX(c) FROM Calc calc2
WHERE Calc.id = Calc2.id)
ORDER BY
id

It is not shortest. But I think that it is very flexible for SQL. It's easy to add new operators. It's easy to change priority of operators.

小开

PHP

Number of characters: 170

Fully obfuscated function:

function a($a,$c='#\(([^()]*)\)#e',$d='a("$1","#^ *-?[\d.]+ *\S *-?[\d.]+ *#e","\$0")'){$e='preg_replace';while($a!=$b=$e($c,$d,$a))$a = $b;return$e('#^(.*)$#e',$d,$a);}

Clearer function:

function a($a, $c = '#\(([^()]*)\)#e', $d = 'a("$1", "#^ *-?[\d.]+ *\S *-?[\d.]+ *#e", "\$0")') {
$e = 'preg_replace';
while ($a != $b = $e($c, $d, $a)) {
$a = $b;
}
return $e('#^(.*)$#e', $d, $a);
}

Tests:

assert(a('1 + 3 / -8') === '-0.5');
assert(a('2*3*4*5+99') === '219');
assert(a('4 * (9 - 4) / (2 * 6 - 2) + 8') === '10');
assert(a('1 + ((123 * 3 - 69) / 100)') === '4');
assert(a('2.45/8.5*9.27+(5*0.0023)') === '2.68344117647');
assert(a(' 2 * 3 * 4 * 5 + 99 ') === '219');

小开

OCaml using Camlp4 directly:

open Camlp4.PreCast


let expr = Gram.Entry.mk "expr"


EXTEND Gram
expr:
[   [ e1 = expr; "+"; e2 = expr -> e1 + e2
| e1 = expr; "-"; e2 = expr -> e1 - e2 ]
|   [ e1 = expr; "*"; e2 = expr -> e1 * e2
| e1 = expr; "/"; e2 = expr -> e1 / e2 ]
|   [ n = INT -> int_of_string n
| "("; e = expr; ")" -> e ]   ];
END


let () = Gram.parse expr Loc.ghost (Stream.of_string "1-2+3*4")

OCaml using the Camlp4 stream parser extension:

open Genlex


let lex = make_lexer ["+"; "-"; "*"; "/"; "("; ")"]


let rec parse_atom = parser
| [< 'Int n >] -> n
| [< 'Kwd "("; e=parse_expr; 'Kwd ")" >] -> e
and parse_factor = parser
| [< e1=parse_atom; stream >] ->
(parser
| [< 'Kwd "*"; e2=parse_factor >] -> e1 * e2
| [< 'Kwd "/"; e2=parse_factor >] -> e1 / e2
| [< >] -> e1) stream
and parse_expr = parser
| [< e1=parse_factor; stream >] ->
(parser
| [< 'Kwd "+"; e2=parse_expr >] -> e1 + e2
| [< 'Kwd "-"; e2=parse_expr >] -> e1 - e2
| [< >] -> e1) stream


let () =
Printf.printf "%d\n" (parse_expr(lex(Stream.of_string "1 + 2 * (3 + 4)")));;

计算一串简单的数学表达式

挑战

规矩

我的解决方案

更新

格式

注意用词

Python

Ruby 1.9

C99

Python

Haskell

JavaScript (Not IE compatible)

C#

C#

Ruby 1.8.7

PHP

Common Lisp

Python 3K

F#

Ruby

Python with regular expressions

C# with Regex Love

F#

Python

Perl

Fortran 77 (gfortran dialect, now with g77 support)

Perl (no eval)

Even shorter

Shorter still

Squeezing water from a stone

Python

Ruby

Python (without importing anything)

J

Number of characters: 208

Visual Basic.NET

Shell script (using sed+awk)

Java

Ruby

MATLAB (v7.8.0)

Assembler

SNOBOL4

Ruby

C++

C# with Regex

C (VS2005)

PowerBASIC

C#, 264 characters

SQL (SQL Server 2008)

Number of characters: 4202

PHP