Build a Command Line Calculator in Objective C with precedence

Urgent help Needed to build simple and very small command line calculator, probably 2 hours of work for good programmers, please help guys I'm stuck on this simple project Specification You are to prepare a MacOS command-line tool that will act as a simple calculator. The a calculator will be run from the command line and will only work with integer numbers and the following arithmetic operators: + - x / % . The % operator is the modulus operator, not percentage. For example, if the program is compiled to calc , the following demonstrates how it will work ./calc 3 + 5 - 7 1 In the command line, the arguments are a repeated sequence in the form [number operator...] and ending in a [number] Hitting the enter key will cause the program to evaluate the arguments and print the result. In this case 1 . The program must follow the usual rules of arithmetic which say: 1. The x / and % operators must all be evaluated before the + and – operators. 2. Operators must be evaluated from left to right. For example, using Rule 1 becomes which results in 2+4*3-6 becomes 2+12-6 which result in 8 If we did not use Rule 1 then 2 + 4 x 3 – 6 would become 6 x 3 – 6 and then 18 – 6 and finally 12 . This is an incorrect result. If we do not use Rule 2 then the following illustrates how it can go wrong 4*5%2 Going from left to right we evaluate the x first, which reduces the expression to 20 % 2 which becomes 0 . If we evaluated the % first then the expression would reduce to 4 x 1 which becomes 4 . This is an incorrect result. Remember, we are using integer mathematics when doing our calculations, so we get integer results when doing division. For example ./calc 20 / 3 6 Also note that we can use the unary + and – operators. For example ./calc -5 / +2 -2 ./calc +2 - -2 4 Your program must also check to make sure the command line arguments are valid. If not your program must generate an appropriate error message and then terminate with non-zero exit status. You should also check for division by zero errors and numeric out-of-bounds errors. As part of your program design, it is expected you will create classes to model the problem domain. Program Hints 1. Getting your program to solve expressions that only use the + and – operators is fairly easy. I would suggest you get your program working at this level before attempting to get it to work with the other operators. 2. While this problem can be solved using iteration, it is easier to solve using recursion.