blob: 1381d7c92c90b54ed910aff292dd061709bc26e7 [file] [log] [blame]
 // run -gcflags=-G=3 // 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 import ( "fmt" "math" ) type Numeric interface { type 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 { type 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 { type complex64, complex128 } // 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] { // TODO(danscales): orderedAbs[T] conversion shouldn't be needed if a < orderedAbs[T](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() { 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)) } }