Evaluate math expression in string? (NSString)

Question

Possible Duplicate:
What is a fast C or Objective-C math parser?

I have a NSString which represents a calculation eg. @"(10+10)*2" and I want to evaluate the string as if it was actually something like this;

double result = (10+10)*2;

What is the most straightforward approach to take in iOS?

Do you mind calling out to another application? `bc` could handle that without much trouble. — Carl Norum, Mar 11 '12 at 00:17
It would implemented on iOS so probably would need to be self contained ? — Chris Bentley, Mar 11 '12 at 00:21
You have a [cocoa] tag - you should probably retag appropriately, then. — Carl Norum, Mar 11 '12 at 00:24
1. Tokenise the input using a lexer. 2. Parse the resulting tokens, build an AST. 3. Evaluate the AST recursively. 4. ???? 5. Profit! — Greg Hewgill, Mar 11 '12 at 00:24
@Itai Ferber: Thanks, Looks like what I need - I'll try them out. — Chris Bentley, Mar 11 '12 at 00:54
[DDMathParser](https://github.com/davedelong/DDMathParser) worked for me on iOS 5 with no problems. Thanks All. — Chris Bentley, Mar 11 '12 at 04:18
you can also do as : http://stackoverflow.com/questions/14436004/arithmetic-operators-and-key-value-coding/14436391#14436391 — Anoop Vaidya, Nov 12 '13 at 13:09
I would recommend the C library [TinyExpr](https://github.com/codeplea/tinyexpr). — 131, Jan 22 '16 at 18:59

score 4 · Accepted Answer · answered Mar 11 '12 at 04:44

4

Take a look at Dave DeLong's DDMathParser framework.

answered Mar 11 '12 at 04:44

Caleb

Thanks. @itai-ferber already pointed to duplicate question which suggests DDMathParser as solution (see comment thread above)... so I already have this working. – Chris Bentley Mar 11 '12 at 05:40

score 2 · Answer 2 · answered Mar 11 '12 at 00:51

2

You can use GCMathParser.

answered Mar 11 '12 at 00:51

pät

This worked out of the box in OS X but I'm having some difficulty getting this to work with iOS 5... It appears to need a little more tweaking that just replacing "#import " with "#import " - I'll look at it again after I check the other suggestions. Thanks. – Chris Bentley Mar 11 '12 at 02:28

2 Answers2