Evaluates simplified s-expressions from the command line using python.
Supported functions: add, multiply
Expression Syntax: ({function} {expression|integer} {expression|integer})
> python calc.py "123"
123
> python calc.py "(add 1 2)"
3
> python calc.py "(multiply 3 (add 1 2))"
9
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My first thought was recursion. This problem seems perfect for it, as you can recursively evaluate expressions, right? Well sure, but the problem is that in order to evaluate a nested expression, you need to match opening and closing parenthesis of outer functions without evaluating inner functions.
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Instead, I was able to loop through each inner function, starting with the first to close. This way I could simply find the first instance of
)and find the nearest(before it to put together an inner function that contained no nested functions, which was easy to evaluate. Keep doing that until all functions are evaluated, and you end up with the final value.