From 078ddecc327a20cec4751e66911197409e01f6d9 Mon Sep 17 00:00:00 2001 From: Dan Scales Date: Tue, 25 Jan 2022 09:50:03 -0800 Subject: [PATCH] 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 Trust: Dan Scales --- test/typeparam/absdiff2.go | 5 +- test/typeparam/absdiff3.go | 82 +++++++++++++++++++++++++++++ test/typeparam/absdiffimp2.dir/a.go | 2 +- 3 files changed, 87 insertions(+), 2 deletions(-) create mode 100644 test/typeparam/absdiff3.go diff --git a/test/typeparam/absdiff2.go b/test/typeparam/absdiff2.go index 8f13bad2b6..2d82c4721c 100644 --- a/test/typeparam/absdiff2.go +++ b/test/typeparam/absdiff2.go @@ -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 diff --git a/test/typeparam/absdiff3.go b/test/typeparam/absdiff3.go new file mode 100644 index 0000000000..3ca03fe26f --- /dev/null +++ b/test/typeparam/absdiff3.go @@ -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)) + } +} diff --git a/test/typeparam/absdiffimp2.dir/a.go b/test/typeparam/absdiffimp2.dir/a.go index 782e000da9..302b69b976 100644 --- a/test/typeparam/absdiffimp2.dir/a.go +++ b/test/typeparam/absdiffimp2.dir/a.go @@ -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 -- 2.48.1