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Clarify specs by defining • as the composition operator
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@sharplet @gfontenot
sharplet authored and gfontenot committed Dec 15, 2015
1 parent 29488bc commit 17a96db
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Showing 5 changed files with 30 additions and 18 deletions.
12 changes: 10 additions & 2 deletions Runes.xcodeproj/project.pbxproj
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Expand Up @@ -17,6 +17,9 @@
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Expand All @@ -35,8 +38,8 @@
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Expand Down Expand Up @@ -92,6 +95,7 @@
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Expand Down Expand Up @@ -267,6 +271,7 @@
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Expand Down Expand Up @@ -561,6 +566,7 @@
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Expand Down Expand Up @@ -591,6 +597,7 @@
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Expand All @@ -601,6 +608,7 @@
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4 changes: 0 additions & 4 deletions Tests/Helpers/Functions.swift
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Expand Up @@ -2,10 +2,6 @@ func id<A>(a: A) -> A {
return a
}

func compose<A, B, C>(f: B -> C, _ g: A -> B) -> A -> C {
return { x in f(g(x)) }
}

func curry<A, B, C>(f: (A, B) -> C) -> A -> B -> C {
return { a in { b in f(a, b) }}
}
8 changes: 8 additions & 0 deletions Tests/Helpers/Operators.swift
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@@ -0,0 +1,8 @@
infix operator • {
associativity right
precedence 170
}

func • <A, B, C> (f: B -> C, g: A -> B) -> A -> C {
return { x in f(g(x)) }
}
12 changes: 6 additions & 6 deletions Tests/Tests/ArraySpec.swift
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Expand Up @@ -18,8 +18,8 @@ class ArraySpec: XCTestCase {
let f = fa.getArrow
let g = fb.getArrow

let lhs = compose(f, g) <^> xs
let rhs = compose(curry(<^>)(f), curry(<^>)(g))(xs)
let lhs = f • g <^> xs
let rhs = (curry(<^>)(f) • curry(<^>)(g))(xs)

return lhs == rhs
}
Expand Down Expand Up @@ -61,7 +61,7 @@ class ArraySpec: XCTestCase {
let g = fb.getArray.map { $0.getArrow }

let lhs = f <*> (g <*> x)
let rhs = pure(curry(compose)) <*> f <*> g <*> x
let rhs = pure(curry(•)) <*> f <*> g <*> x

return lhs == rhs
}
Expand All @@ -70,7 +70,7 @@ class ArraySpec: XCTestCase {
func testMonad() {
// return x >>= f = f x
property("left identity law") <- forAll { (x: Int, fa: ArrowOf<Int, Int>) in
let f: Int -> [Int] = compose(pure, fa.getArrow)
let f: Int -> [Int] = pure • fa.getArrow

let lhs = pure(x) >>- f
let rhs = f(x)
Expand All @@ -89,8 +89,8 @@ class ArraySpec: XCTestCase {
// (m >>= f) >>= g = m >>= (\x -> f x >>= g)
property("associativity law") <- forAll { (a: ArrayOf<Int>, fa: ArrowOf<Int, Int>, fb: ArrowOf<Int, Int>) in
let m = a.getArray
let f: Int -> [Int] = compose(pure, fa.getArrow)
let g: Int -> [Int] = compose(pure, fb.getArrow)
let f: Int -> [Int] = pure • fa.getArrow
let g: Int -> [Int] = pure • fb.getArrow

let lhs = (m >>- f) >>- g
let rhs = m >>- { x in f(x) >>- g }
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12 changes: 6 additions & 6 deletions Tests/Tests/OptionalSpec.swift
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Expand Up @@ -18,8 +18,8 @@ class OptionalSpec: XCTestCase {
let g = fb.getArrow
let x = o.getOptional

let lhs = compose(f, g) <^> x
let rhs = compose(curry(<^>)(f), curry(<^>)(g))(x)
let lhs = f • g <^> x
let rhs = (curry(<^>)(f) • curry(<^>)(g))(x)

return lhs == rhs
}
Expand Down Expand Up @@ -61,7 +61,7 @@ class OptionalSpec: XCTestCase {
let g = fb.getOptional?.getArrow

let lhs = f <*> (g <*> x)
let rhs = pure(curry(compose)) <*> f <*> g <*> x
let rhs = pure(curry(•)) <*> f <*> g <*> x

return lhs == rhs
}
Expand All @@ -70,7 +70,7 @@ class OptionalSpec: XCTestCase {
func testMonad() {
// return x >>= f = f x
property("left identity law") <- forAll { (x: Int, fa: ArrowOf<Int, Int>) in
let f: Int -> Int? = compose(pure, fa.getArrow)
let f: Int -> Int? = pure • fa.getArrow

let lhs = pure(x) >>- f
let rhs = f(x)
Expand All @@ -91,8 +91,8 @@ class OptionalSpec: XCTestCase {
// (m >>= f) >>= g = m >>= (\x -> f x >>= g)
property("associativity law") <- forAll { (o: OptionalOf<Int>, fa: ArrowOf<Int, Int>, fb: ArrowOf<Int, Int>) in
let m = o.getOptional
let f: Int -> Int? = compose(pure, fa.getArrow)
let g: Int -> Int? = compose(pure, fb.getArrow)
let f: Int -> Int? = pure • fa.getArrow
let g: Int -> Int? = pure • fb.getArrow

let lhs = (m >>- f) >>- g
let rhs = m >>- { x in f(x) >>- g }
Expand Down

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