Playing With Compare And Closures

// playing with compare() and closures

import Foundation

print("actOn start")

let one = "1"

let two = "2"

func actOn(_ result: ComparisonResult, 

        ifLess: ()->Void, 

        ifEqual: ()->Void, 

        ifGreater: ()->Void ) {

    switch result {

        case .orderedAscending:

            ifLess()

        case .orderedSame:

            ifEqual()

        case .orderedDescending:

            ifGreater()

    }

}

actOn(one.compare(two), ifLess: {print("    string 1 < 2")},

        ifEqual: {print("    string 1 == 2")},

        ifGreater: {print("    string 1 > 2")})

actOn(two.compare(two), ifLess: {print("    string 2 < 2")},

        ifEqual: {print("    string 2 == 2")},

        ifGreater: {print("    string 2 > 2")})

actOn(two.compare(one), ifLess: {print("    string 2 < 1")},

        ifEqual: {print("    string 2 == 1")},

        ifGreater: {print("    string 2 > 1")})

print("actOn end\n")

print("switch start")

switch one.compare(two) {

    case .orderedAscending:   print("    switch 1 < 2")

    case .orderedSame:        print("    switch 1 == 2")

    case .orderedDescending:  print("    switch 1 > 2")

}

switch two.compare(two) {

    case .orderedAscending:

        print("    switch 2 < 2")

    case .orderedSame:

        print("    switch 2 == 2")

    case .orderedDescending:

        print("    switch 2 > 2")

}

switch two.compare(one) {

    case .orderedAscending:

        print("    switch 2 < 1")

    case .orderedSame:

        print("    switch 2 == 1")

    case .orderedDescending:

        print("    switch 2 > 1")

}

print("switch end\n")

print("compare start")

func compareComparable

>(_ expr1: T, _ expr2: T, ifLess: ()->Void, ifEqual: ()->Void, ifGreater: ()->Void ) {

    if expr1 < expr2 {

        ifLess()

    }

    else if expr1 == expr2 {

        ifEqual()

    }

    else if expr1 > expr2 {

        ifGreater()

    }

    else {

       assertionFailure("\(expr1) isn't < or == or > \(expr2)")

    }

}

compare(1, 2,  ifLess:     {print("    1 < 2")},

               ifEqual:    {print("    1 == 2")},

               ifGreater:  {print("    1 > 2")})

compare(2, 2, ifLess: {print("    2 < 2")},

    ifEqual: {print("    2 == 2")},

    ifGreater: {print("    2 > 2")})

compare(2, 1, ifLess: {print("    2 < 1")},

    ifEqual: {print("    2 == 1")},

    ifGreater: {print("    2 > 1")})

// trigger assertion (as designed)

compare(Double.nan, Double.leastNonzeroMagnitude, ifLess: {print("NaN < n")},

    ifEqual: {print("    NaN == n")},

    ifGreater: {print("    NaN > n")})

print("compare end\n")

----------- output -------------------------------------------------------

actOn start

    string 1 < 2

    string 2 == 2

    string 2 > 1

actOn end

switch start

    switch 1 < 2

    switch 2 == 2

    switch 2 > 1

switch end

compare start

    1 < 2

    2 == 2

    2 > 1

fatal error: nan isn't < or == or > 4.94065645841247e-324: file forloop.playground, line 76