blob: 361708f1ebb1df0ea3a1678de8b3f7b32be24aca [file] [log] [blame]
 // run // Copyright 2021 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package main import ( "fmt" ) type Gen[A any] func() (A, bool) func Combine[T1, T2, T any](g1 Gen[T1], g2 Gen[T2], join func(T1, T2) T) Gen[T] { return func() (T, bool) { var t T t1, ok := g1() if !ok { return t, false } t2, ok := g2() if !ok { return t, false } return join(t1, t2), true } } type Pair[A, B any] struct { A A B B } func _NewPair[A, B any](a A, b B) Pair[A, B] { return Pair[A, B]{a, b} } func Combine2[A, B any](ga Gen[A], gb Gen[B]) Gen[Pair[A, B]] { return Combine(ga, gb, _NewPair[A, B]) } func main() { var g1 Gen[int] = func() (int, bool) { return 3, true } var g2 Gen[string] = func() (string, bool) { return "x", false } var g3 Gen[string] = func() (string, bool) { return "y", true } gc := Combine(g1, g2, _NewPair[int, string]) if got, ok := gc(); ok { panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok)) } gc2 := Combine2(g1, g2) if got, ok := gc2(); ok { panic(fmt.Sprintf("got %v, %v, wanted -/false", got, ok)) } gc3 := Combine(g1, g3, _NewPair[int, string]) if got, ok := gc3(); !ok || got.A != 3 || got.B != "y" { panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok)) } gc4 := Combine2(g1, g3) if got, ok := gc4(); !ok || got.A != 3 || got.B != "y" { panic(fmt.Sprintf("got %v, %v, wanted {3, y}, true", got, ok)) } }