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078ddecc32
We have disallowed having a typeparam on the right-hand-side of a type declaration. So, we disabled much of the test absdiff.go. I recently wrote a new test absdiff2.go to use a structure containing the type param type, so I could attach a method properly and run the full test. As a contrast, I thought I would create absdiff3.go, where the Abs functionality is passed in as a function callback (but derived from a generic function). This is simpler, and more inline with some of the guidelines that Ian has been proposing (use passed-in functions rather than requiring methods, when possible, for greater ease-of-use). Only adds a new test absdiff3.go. (And fixes a comment in absdiff2.go.) Change-Id: I6dd185b50a3baeec31f689a892319963468a7201 Reviewed-on: https://go-review.googlesource.com/c/go/+/380774 Reviewed-by: Robert Griesemer <gri@golang.org> Trust: Dan Scales <danscales@google.com>
83 lines
2.2 KiB
Go
83 lines
2.2 KiB
Go
// run -gcflags=-G=3
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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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// absdiff example using a function argument rather than attaching an
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// Abs method to a structure containing base types.
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package main
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import (
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"fmt"
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"math"
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)
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type Numeric interface {
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OrderedNumeric | Complex
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}
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// absDifference computes the absolute value of the difference of
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// a and b, where the absolute value is determined by the abs function.
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func absDifference[T Numeric](a, b T, abs func(a T) T) T {
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return abs(a - b)
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}
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// OrderedNumeric matches numeric types that support the < operator.
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type OrderedNumeric interface {
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~int | ~int8 | ~int16 | ~int32 | ~int64 |
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~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
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~float32 | ~float64
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}
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func Abs[T OrderedNumeric](a T) T {
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if a < 0 {
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return -a
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}
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return a
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}
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// Complex matches the two complex types, which do not have a < operator.
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type Complex interface {
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~complex64 | ~complex128
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}
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func ComplexAbs[T Complex](a T) T {
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r := float64(real(a))
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i := float64(imag(a))
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d := math.Sqrt(r*r + i*i)
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return T(complex(d, 0))
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}
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// OrderedAbsDifference returns the absolute value of the difference
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// between a and b, where a and b are of an ordered type.
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func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
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return absDifference(a, b, Abs[T])
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}
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// ComplexAbsDifference returns the absolute value of the difference
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// between a and b, where a and b are of a complex type.
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func ComplexAbsDifference[T Complex](a, b T) T {
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return absDifference(a, b, ComplexAbs[T])
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}
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func main() {
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if got, want := OrderedAbsDifference(1.0, -2.0), 3.0; got != want {
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panic(fmt.Sprintf("got = %v, want = %v", got, want))
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}
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if got, want := OrderedAbsDifference(-1.0, 2.0), 3.0; got != want {
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panic(fmt.Sprintf("got = %v, want = %v", got, want))
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}
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if got, want := OrderedAbsDifference(-20, 15), 35; got != want {
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panic(fmt.Sprintf("got = %v, want = %v", got, want))
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}
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if got, want := ComplexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
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panic(fmt.Sprintf("got = %v, want = %v", got, want))
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}
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if got, want := ComplexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
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panic(fmt.Sprintf("got = %v, want = %v", got, want))
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}
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}
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