blob: 9c83effbda4f2b6b8f0fd8d89004a86f4db9c19e [file] [log] [blame]
 // run // Copyright 2020 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. package main type Numeric interface { ~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~float32 | ~float64 | ~complex64 | ~complex128 } // numericAbs matches numeric types with an Abs method. type numericAbs[T any] interface { Numeric Abs() T } // 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 numericAbs[T]](a, b T) T { d := a - b return d.Abs() } // orderedNumeric matches numeric types that support the < operator. type orderedNumeric interface { ~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~float32 | ~float64 } // Complex matches the two complex types, which do not have a < operator. type Complex interface { ~complex64 | ~complex128 } // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639). // // orderedAbs is a helper type that defines an Abs method for // // ordered numeric types. // type orderedAbs[T orderedNumeric] T // // func (a orderedAbs[T]) Abs() orderedAbs[T] { // if a < 0 { // return -a // } // return a // } // // // complexAbs is a helper type that defines an Abs method for // // complex types. // type complexAbs[T Complex] T // // func (a complexAbs[T]) Abs() complexAbs[T] { // r := float64(real(a)) // i := float64(imag(a)) // d := math.Sqrt(r*r + i*i) // return complexAbs[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 T(absDifference(orderedAbs[T](a), orderedAbs[T](b))) // } // // // 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 T(absDifference(complexAbs[T](a), complexAbs[T](b))) // } func main() { // // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639). // 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)) // } }