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// Copyright 2023 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 cmp provides types and functions related to comparing
// ordered values.
package cmp
// Ordered is a constraint that permits any ordered type: any type
// that supports the operators < <= >= >.
// If future releases of Go add new ordered types,
// this constraint will be modified to include them.
//
// Note that floating-point types may contain NaN ("not-a-number") values.
// An operator such as == or < will always report false when
// comparing a NaN value with any other value, NaN or not.
// See the [Compare] function for a consistent way to compare NaN values.
type Ordered interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
~float32 | ~float64 |
~string
}
// Less reports whether x is less than y.
// For floating-point types, a NaN is considered less than any non-NaN,
// and -0.0 is not less than (is equal to) 0.0.
func Less[T Ordered](x, y T) bool {
return (isNaN(x) && !isNaN(y)) || x < y
}
// Compare returns
//
// -1 if x is less than y,
// 0 if x equals y,
// +1 if x is greater than y.
//
// For floating-point types, a NaN is considered less than any non-NaN,
// a NaN is considered equal to a NaN, and -0.0 is equal to 0.0.
func Compare[T Ordered](x, y T) int {
xNaN := isNaN(x)
yNaN := isNaN(y)
if xNaN && yNaN {
return 0
}
if xNaN || x < y {
return -1
}
if yNaN || x > y {
return +1
}
return 0
}
// isNaN reports whether x is a NaN without requiring the math package.
// This will always return false if T is not floating-point.
func isNaN[T Ordered](x T) bool {
return x != x
}
// Or returns the first of its arguments that is not equal to the zero value.
// If no argument is non-zero, it returns the zero value.
func Or[T comparable](vals ...T) T {
var zero T
for _, val := range vals {
if val != zero {
return val
}
}
return zero
}
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