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test: add a new test absdiff3.go which uses function callback

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>
This commit is contained in:
Dan Scales 2022-01-25 09:50:03 -08:00
parent 16d6a5233a
commit 078ddecc32
3 changed files with 87 additions and 2 deletions

View File

@ -4,6 +4,9 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// absdiff example in which an Abs method is attached to a generic type, which is a
// structure with a single field that may be a list of possible basic types.
package main
import (
@ -24,7 +27,7 @@ type numericAbs[T Numeric] interface {
Abs() T
}
// AbsDifference computes the absolute value of the difference of
// absDifference computes the absolute value of the difference of
// a and b, where the absolute value is determined by the Abs method.
func absDifference[T Numeric, U numericAbs[T]](a, b U) T {
d := a.Value - b.Value

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@ -0,0 +1,82 @@
// run -gcflags=-G=3
// Copyright 2022 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.
// absdiff example using a function argument rather than attaching an
// Abs method to a structure containing base types.
package main
import (
"fmt"
"math"
)
type Numeric interface {
OrderedNumeric | Complex
}
// absDifference computes the absolute value of the difference of
// a and b, where the absolute value is determined by the abs function.
func absDifference[T Numeric](a, b T, abs func(a T) T) T {
return abs(a - b)
}
// OrderedNumeric matches numeric types that support the < operator.
type OrderedNumeric interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
~float32 | ~float64
}
func Abs[T OrderedNumeric](a T) T {
if a < 0 {
return -a
}
return a
}
// Complex matches the two complex types, which do not have a < operator.
type Complex interface {
~complex64 | ~complex128
}
func ComplexAbs[T Complex](a T) T {
r := float64(real(a))
i := float64(imag(a))
d := math.Sqrt(r*r + i*i)
return T(complex(d, 0))
}
// OrderedAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of an ordered type.
func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
return absDifference(a, b, Abs[T])
}
// ComplexAbsDifference returns the absolute value of the difference
// between a and b, where a and b are of a complex type.
func ComplexAbsDifference[T Complex](a, b T) T {
return absDifference(a, b, ComplexAbs[T])
}
func main() {
if got, want := OrderedAbsDifference(1.0, -2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := OrderedAbsDifference(-1.0, 2.0), 3.0; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := OrderedAbsDifference(-20, 15), 35; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := ComplexAbsDifference(5.0+2.0i, 2.0-2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
if got, want := ComplexAbsDifference(2.0-2.0i, 5.0+2.0i), 5+0i; got != want {
panic(fmt.Sprintf("got = %v, want = %v", got, want))
}
}

View File

@ -21,7 +21,7 @@ type numericAbs[T Numeric] interface {
Abs() T
}
// AbsDifference computes the absolute value of the difference of
// absDifference computes the absolute value of the difference of
// a and b, where the absolute value is determined by the Abs method.
func absDifference[T Numeric, U numericAbs[T]](a, b U) T {
d := a.Value - b.Value