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// run
// 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 realimag(x any) (re, im float64) {
switch z := x.(type) {
case complex64:
re = float64(real(z))
im = float64(imag(z))
case complex128:
re = real(z)
im = imag(z)
default:
panic("unknown complex type")
}
return
}
func ComplexAbs[T Complex](a T) T {
// TODO use direct conversion instead of realimag once #50937 is fixed
r, i := realimag(a)
// 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))
}
}
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