the code can paraser Exp and calculate result

support baseOperater: + - * / % ^
the '^' is cube
support moreFuction: sin cos tan cot sec csc log ln sqrt
the 'log' baseNumber is 2
the 'ln' baseNumber is e
support sepcConstant: pi e
support brakets: () [] {}

NSLog(@"%@",[GHExpParser parserExp:@"3+(4*5)-2^2"]); // ok

NSLog(@"%@",[GHExpParser parserExp:@"3+[(4*5)-2]-sin(PI/2)"]); // ok

NSLog(@"%@",[GHExpParser parserExp:@"6%4"]); // ok

NSLog(@"%@",[GHExpParser parserExp:@"(2+3*5"]); //error return nil

NSLog(@"%@",[GHExpParser parserExp:@"3*4+2)"]); //error

NSLog(@"%@",[GHExpParser parserExp:@"3*((4+2)"]); //error

NSLog(@"%@",[GHExpParser parserExp:@"3*/4+2"]); //error

NSLog(@"%@",[GHExpParser parserExp:@"3*x+2"]); //error not support alphabet

NSLog(@"%@",[GHExpParser parserExp:@"3+sinPI/2"]);// is equal sinPi / 2 not sin(Pi/2)

NSLog(@"%@",[GHExpParser parserExp:@"3+sin(PI/2)"]);// real sin(Pi/2)

NSLog(@"%@",[GHExpParser parserExp:@"3+SInPi/2"]);// ignore capitalized or lowercase