Calcurator

Calculator.swift

import Foundation

func parseExpression(tokens:[String]) -> [String] {
    let operators:[String:Int] = [
        "*": 10,
        "/": 10,
        "+": 9,
        "-": 9,
        "(": 0,
        ")": 0
    ]
    var output:Array<String> = []
    var stack:Array<String> = []
    for token in tokens {
        switch token {
        case ")":
            while !stack.isEmpty {
                let p = stack.removeLast()
                if p == "(" {
                    break
                } else {
                    output.append(p)
                }
            }
        case "(":
            stack.append(token)
        default:
            if contains(operators.keys, token) {
                while !stack.isEmpty {
                    if operators[stack.last!]! >= operators[token]! {
                        output.append(stack.removeLast())
                    } else {
                        break
                    }
                }
                stack.append(token)
            } else {
                output.append(token)
            }
        }
    }
    while !stack.isEmpty {
        output.append(stack.removeLast())
    }
    return output
}

func calculateTokens(var tokens:[String]) -> Double {
    let operators:[String:(Double, Double) -> Double] = [
        "*" : (*),
        "/" : (/),
        "+" : (+),
        "-" : (-)
    ]

    var stack:[Double] = []
    
    func performOperation(operation:(Double, Double) -> Double) -> Double {
        let rhs = stack.removeLast()
        let lhs = stack.removeLast()
        let result = operation(lhs, rhs)
        stack.append(result)
        return result
    }

    for token in tokens {
        if !contains(operators.keys, token) {
            if let number = NSNumberFormatter().numberFromString(token) {
                stack.append(number.doubleValue)
            }
        }
        else {
            let r = performOperation(operators[token]!)
            //println(r)
        }
    }

    return stack.removeLast()
}





let e = split("( 1 + 2 ) * 3 - 2", isSeparator:{$0 == " "})
let r = parseExpression(e)
let rr = calculateTokens(r)
println(r)
println(rr)