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https://github.com/golang/go
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b8248fab89
This is a feature that is not understood well enough and may have subtle repercussions impacting future changes. Disable for Go 1.18. The actual change is trivial: disable a branch through a flag. The remaining changes are adjustments to tests. Fixes #51576. Change-Id: Ib77b038b846711a808315a8889b3904e72367bce Reviewed-on: https://go-review.googlesource.com/c/go/+/391135 Trust: Robert Griesemer <gri@golang.org> Run-TryBot: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
76 lines
1.6 KiB
Go
76 lines
1.6 KiB
Go
// run
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// Copyright 2022 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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// license that can be found in the LICENSE file.
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package main
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import (
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"fmt"
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)
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// Numeric expresses a type constraint satisfied by any numeric type.
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type Numeric interface {
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~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 |
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~int | ~int8 | ~int16 | ~int32 | ~int64 |
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~float32 | ~float64 |
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~complex64 | ~complex128
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}
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// Sum returns the sum of the provided arguments.
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func Sum[T Numeric](args ...T) T {
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var sum T
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for i := 0; i < len(args); i++ {
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sum += args[i]
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}
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return sum
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}
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// Ledger is an identifiable, financial record.
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type Ledger[T ~string, K Numeric] struct {
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// ID identifies the ledger.
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ID_ T
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// Amounts is a list of monies associated with this ledger.
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Amounts_ []K
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// SumFn is a function that can be used to sum the amounts
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// in this ledger.
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SumFn_ func(...K) K
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}
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// Field accesses through type parameters are disabled
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// until we have a more thorough understanding of the
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// implications on the spec. See issue #51576.
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// Use accessor methods instead.
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func (l Ledger[T, _]) ID() T { return l.ID_ }
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func (l Ledger[_, K]) Amounts() []K { return l.Amounts_ }
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func (l Ledger[_, K]) SumFn() func(...K) K { return l.SumFn_ }
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func PrintLedger[
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T ~string,
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K Numeric,
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L interface {
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~struct {
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ID_ T
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Amounts_ []K
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SumFn_ func(...K) K
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}
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ID() T
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Amounts() []K
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SumFn() func(...K) K
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},
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](l L) {
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fmt.Printf("%s has a sum of %v\n", l.ID(), l.SumFn()(l.Amounts()...))
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}
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func main() {
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PrintLedger(Ledger[string, int]{
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ID_: "fake",
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Amounts_: []int{1, 2, 3},
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SumFn_: Sum[int],
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})
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}
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