linalg.go

     1  // Copyright 2019 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 linalg
     6  
     7  // Numeric is type bound that matches any numeric type.
     8  // It would likely be in a constraints package in the standard library.
     9  type Numeric interface {
    10  	~int | ~int8 | ~int16 | ~int32 | ~int64 |
    11  		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
    12  		~float32 | ~float64 |
    13  		~complex64 | ~complex128
    14  }
    15  
    16  func DotProduct[T Numeric](s1, s2 []T) T {
    17  	if len(s1) != len(s2) {
    18  		panic("DotProduct: slices of unequal length")
    19  	}
    20  	var r T
    21  	for i := range s1 {
    22  		r += s1[i] * s2[i]
    23  	}
    24  	return r
    25  }
    26  
    27  // NumericAbs matches numeric types with an Abs method.
    28  type NumericAbs[T any] interface {
    29  	Numeric
    30  
    31  	Abs() T
    32  }
    33  
    34  // AbsDifference computes the absolute value of the difference of
    35  // a and b, where the absolute value is determined by the Abs method.
    36  func AbsDifference[T NumericAbs[T]](a, b T) T {
    37  	d := a - b
    38  	return d.Abs()
    39  }
    40  
    41  // OrderedNumeric is a type bound that matches numeric types that support the < operator.
    42  type OrderedNumeric interface {
    43  	~int | ~int8 | ~int16 | ~int32 | ~int64 |
    44  		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
    45  		~float32 | ~float64
    46  }
    47  
    48  // Complex is a type bound that matches the two complex types, which do not have a < operator.
    49  type Complex interface {
    50  	~complex64 | ~complex128
    51  }
    52  
    53  // For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
    54  // // OrderedAbs is a helper type that defines an Abs method for
    55  // // ordered numeric types.
    56  // type OrderedAbs[T OrderedNumeric] T
    57  // 
    58  // func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
    59  // 	if a < 0 {
    60  // 		return -a
    61  // 	}
    62  // 	return a
    63  // }
    64  // 
    65  // // ComplexAbs is a helper type that defines an Abs method for
    66  // // complex types.
    67  // type ComplexAbs[T Complex] T
    68  // 
    69  // func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
    70  // 	r := float64(real(a))
    71  // 	i := float64(imag(a))
    72  // 	d := math.Sqrt(r * r + i * i)
    73  // 	return ComplexAbs[T](complex(d, 0))
    74  // }
    75  // 
    76  // func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
    77  // 	return T(AbsDifference(OrderedAbs[T](a), OrderedAbs[T](b)))
    78  // }
    79  // 
    80  // func ComplexAbsDifference[T Complex](a, b T) T {
    81  // 	return T(AbsDifference(ComplexAbs[T](a), ComplexAbs[T](b)))
    82  // }
    83
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