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import SwiftCheck
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2
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import Bow
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3
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import BowGenerators
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4
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5
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public class FunctorLaws<F: Functor & EquatableK & ArbitraryK> {
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6
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public static func check() {
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7
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InvariantLaws<F>.check()
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8
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covariantIdentity()
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9
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covariantComposition()
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10
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void()
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11
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fproduct()
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12
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tupleLeft()
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13
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tupleRight()
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14
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}
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15
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16
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private static func covariantIdentity() {
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17
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property("Identity is preserved under functor transformation") <~ forAll() { (fa: KindOf<F, Int>) in
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18
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return F.map(fa.value, id) == id(fa.value)
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19
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}
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20
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}
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21
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22
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private static func covariantComposition() {
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23
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property("Composition is preserved under functor transformation") <~ forAll() { (fa: KindOf<F, Int>, f: ArrowOf<Int, Int>, g: ArrowOf<Int, Int>) in
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24
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return F.map(F.map(fa.value, f.getArrow), g.getArrow) ==
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25
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F.map(fa.value, f.getArrow >>> g.getArrow)
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26
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}
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27
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}
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28
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29
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private static func void() {
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30
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property("Void") <~ forAll() { (fa: KindOf<F, Int>, f: ArrowOf<Int, Int>) in
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31
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return isEqual(F.void(fa.value), F.void(F.map(fa.value, f.getArrow)))
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32
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}
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33
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}
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34
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35
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private static func fproduct() {
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36
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property("fproduct") <~ forAll { (fa: KindOf<F, Int>, f: ArrowOf<Int, Int>) in
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37
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return F.map(F.fproduct(fa.value, f.getArrow), { x in x.1 }) ==
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38
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F.map(fa.value, f.getArrow)
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39
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}
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40
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}
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41
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42
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private static func tupleLeft() {
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43
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property("tuple left") <~ forAll { (fa: KindOf<F, Int>, b: Int) in
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44
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return F.map(F.tupleLeft(fa.value, b), { x in x.0 }) ==
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45
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F.as(fa.value, b)
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46
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}
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47
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}
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48
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49
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1
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private static func tupleRight() {
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50
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property("tuple right") <~ forAll { (fa: KindOf<F, Int>, b: Int) in
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51
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return F.map(F.tupleRight(fa.value, b), { x in x.1 }) ==
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52
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F.as(fa.value, b)
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53
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}
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54
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}
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55
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}
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truizlop