Objective c operations with variables

Question

Is there a relatively easy way to use mathematical operators with string variables in Objective C?

For example:

The string "x*x" should return "x^2"

The string "x/x" should return "1"

I'm looking for something that would actually use the variable name "x" without an assigned numerical value and return an answer in terms of "x".

Answer 1

If you put the 'x' value as string then you can evaluate it as :

NSString *string=@"3*3";
NSExpression *expression = [NSExpression expressionWithFormat:string];
float result = [[expression expressionValueWithObject:nil context:nil] floatValue];
NSLog(@"%f", result);

Also,

NSString *string=@"34*(2.56+1.79)-42/1.5";
NSNumber *result=[NSExpression expressionWithFormat:string];
NSLog(@"%@", result);

Change to any datatype float to int etc as per your requirement

Answer 2

I've had a look for an Objective C lib doing algebraic manipulation and haven't found much yet.

So your best bet might be to use a C library (Objective C is a superset of ANSI C, after all, and you can mix the the two).

Check out this list of C maths libs:

http://www.mathtools.net/C_C__/Mathematics/

From that list, it seems that Mathomatic might be of use.

Two strategies for using a C library in your Objective C:

1. Just call the C functions from your Objective C code

2. Create an Objective C wrapper for the C library and use that (and maybe release it for others to use :)