a.go

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package a
     6  
     7  type Numeric interface {
     8  	~int | ~int8 | ~int16 | ~int32 | ~int64 |
     9  		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
    10  		~float32 | ~float64 |
    11  		~complex64 | ~complex128
    12  }
    13  
    14  // numericAbs matches numeric types with an Abs method.
    15  type numericAbs[T any] interface {
    16  	Numeric
    17  	Abs() T
    18  }
    19  
    20  // AbsDifference computes the absolute value of the difference of
    21  // a and b, where the absolute value is determined by the Abs method.
    22  func absDifference[T numericAbs[T]](a, b T) T {
    23  	d := a - b
    24  	return d.Abs()
    25  }
    26  
    27  // orderedNumeric matches numeric types that support the < operator.
    28  type orderedNumeric interface {
    29  	~int | ~int8 | ~int16 | ~int32 | ~int64 |
    30  		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
    31  		~float32 | ~float64
    32  }
    33  
    34  // Complex matches the two complex types, which do not have a < operator.
    35  type Complex interface {
    36  	~complex64 | ~complex128
    37  }
    38  
    39  // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
    40  // // orderedAbs is a helper type that defines an Abs method for
    41  // // ordered numeric types.
    42  // type orderedAbs[T orderedNumeric] T
    43  //
    44  // func (a orderedAbs[T]) Abs() orderedAbs[T] {
    45  // 	if a < 0 {
    46  // 		return -a
    47  // 	}
    48  // 	return a
    49  // }
    50  //
    51  // // complexAbs is a helper type that defines an Abs method for
    52  // // complex types.
    53  // type complexAbs[T Complex] T
    54  //
    55  // func (a complexAbs[T]) Abs() complexAbs[T] {
    56  // 	r := float64(real(a))
    57  // 	i := float64(imag(a))
    58  // 	d := math.Sqrt(r*r + i*i)
    59  // 	return complexAbs[T](complex(d, 0))
    60  // }
    61  //
    62  // // OrderedAbsDifference returns the absolute value of the difference
    63  // // between a and b, where a and b are of an ordered type.
    64  // func OrderedAbsDifference[T orderedNumeric](a, b T) T {
    65  // 	return T(absDifference(orderedAbs[T](a), orderedAbs[T](b)))
    66  // }
    67  //
    68  // // ComplexAbsDifference returns the absolute value of the difference
    69  // // between a and b, where a and b are of a complex type.
    70  // func ComplexAbsDifference[T Complex](a, b T) T {
    71  // 	return T(absDifference(complexAbs[T](a), complexAbs[T](b)))
    72  // }
    73
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