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5355753009
We don't usually reformat the test directory, but all of the files in test/typeparam are syntactically valid. I suspect the misformattings here are because developers aren't re-installing gofmt with -tags=typeparams, not intentionally exercising non-standard formatting. Change-Id: I3767d480434c19225568f3c7d656dc8589197183 Reviewed-on: https://go-review.googlesource.com/c/go/+/338093 Trust: Matthew Dempsky <mdempsky@google.com> Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
100 lines
2 KiB
Go
100 lines
2 KiB
Go
// run -gcflags=-G=3
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// lice
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package main
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import "fmt"
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// Overriding the predeclare "any", so it can be used as a type constraint or a type
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// argument
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type any interface{}
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type Function[a, b any] interface {
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Apply(x a) b
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}
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type incr struct{ n int }
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func (this incr) Apply(x int) int {
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return x + this.n
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}
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type pos struct{}
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func (this pos) Apply(x int) bool {
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return x > 0
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}
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type compose[a, b, c any] struct {
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f Function[a, b]
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g Function[b, c]
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}
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func (this compose[a, b, c]) Apply(x a) c {
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return this.g.Apply(this.f.Apply(x))
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}
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type _Eq[a any] interface {
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Equal(a) bool
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}
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type Int int
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func (this Int) Equal(that int) bool {
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return int(this) == that
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}
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type List[a any] interface {
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Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any
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}
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type Nil[a any] struct {
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}
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func (xs Nil[a]) Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any {
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return casenil.Apply(xs)
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}
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type Cons[a any] struct {
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Head a
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Tail List[a]
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}
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func (xs Cons[a]) Match(casenil Function[Nil[a], any], casecons Function[Cons[a], any]) any {
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return casecons.Apply(xs)
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}
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type mapNil[a, b any] struct {
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}
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func (m mapNil[a, b]) Apply(_ Nil[a]) any {
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return Nil[b]{}
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}
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type mapCons[a, b any] struct {
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f Function[a, b]
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}
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func (m mapCons[a, b]) Apply(xs Cons[a]) any {
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return Cons[b]{m.f.Apply(xs.Head), Map[a, b](m.f, xs.Tail)}
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}
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func Map[a, b any](f Function[a, b], xs List[a]) List[b] {
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return xs.Match(mapNil[a, b]{}, mapCons[a, b]{f}).(List[b])
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}
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func main() {
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var xs List[int] = Cons[int]{3, Cons[int]{6, Nil[int]{}}}
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var ys List[int] = Map[int, int](incr{-5}, xs)
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var xz List[bool] = Map[int, bool](pos{}, ys)
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cs1 := xz.(Cons[bool])
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cs2 := cs1.Tail.(Cons[bool])
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_, ok := cs2.Tail.(Nil[bool])
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if cs1.Head != false || cs2.Head != true || !ok {
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panic(fmt.Sprintf("got %v, %v, %v, expected false, true, true",
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cs1.Head, cs2.Head, ok))
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}
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}
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