calculator.h

#ifndef CALCULATOR_H
#define CALCULATOR_H

#include <string>

/*
returns precedence of the operator
input: c - a character representing an operator, e.g. '+'
output: the corresponding value of that operator's precedence, e.g. 2
throws: none
*/
int precedence (wchar_t c);

/*
checks if a wchar_t is an operator
input: c - any character
output: true if the character is one of the four operators, false otherwise
throws: none
*/
bool isOperator (wchar_t c);

/*
checks if the expression is valid
input: s - a wstring representing an expression, e.g. '(1+2)'
output: true if the expression is valid, false otherwise
throws: none.
*/
bool validate (std::wstring s);

/*
changes an infix expression to its postfix form
input: s - a wstring representing an expression, e.g. '(1+2)'
output: postfix form of the expression, e.g. '1 2 +
throws: none.
*/
std::wstring postfix (std::wstring s);

/*
standardizes input
input: s - a wstring representing an expression, e.g. '(1 + 2)'
output: the wstring expression without any spaces, e.g. '(1+2)'
throws: none.
*/
std::wstring standardize (std::wstring s);

/*
computes the result of an expression
input: s - a wstring representing an expression, e.g. '(1+2)'
output: the result of the arithmetic expression, e.g. '3'
throws: std::invalid_argument if the expression is incomplete, e.g. '(1+)'
*/
std::wstring calculate (std::wstring s);

#endif  // CALCULATOR_H