Executing NSStrings ???

[cation007]

Hi,
dont know if this is a good question or a stupid question.

How do I execute a string ? say like,

NSString *mystring = @"3.2+5.7";

float sum = mystring;

<mystring> has to be executed and stored to sum. Is it even possible in Obj C ?

I have done that with PERL and shell scripting ...

Thanks,