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// run -gcflags=-G=3
// 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))
}
}
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