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ix.go
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ix.go
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// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package ix contains small integer arithmetic functions in the style of the standard `math` package.
package ix
type signed interface {
~int | ~int8 | ~int16 | ~int32 | ~int64
}
type unsigned interface {
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
}
type integer interface {
signed | unsigned
}
// Abs returns the absolute value of x.
func Abs[T signed](x T) T {
if x < 0 {
return -x
}
return x
}
// Sign returns -1, 0 or 1 if x is less than, equal, or greater than zero, respectively.
func Sign[T signed](x T) T {
if x < 0 {
return -1
} else if x > 0 {
return 1
}
return 0
}
// CeilDiv returns the result of the integer division a / b except rounded up (for nonnegative integers).
func CeilDiv[T integer](a, b T) T {
return (a + b - 1) / b
}
// GCD returns the greatest common divisor of the two arguments.
func GCD[T integer](a, b T) T {
for b != 0 {
t := b
b = a % b
a = t
}
return a
}
// LCM returns the least common multiple of the two arguments.
func LCM[T integer](a, b T) T {
return a / GCD(a, b) * b
}
// Sqrt returns the integer square root of y. For a nonnegative argument,
// it is the floor of the mathematical square root. Panics for negative numbers.
func Sqrt(y int) int {
if y < 0 {
panic("sqrt(neg)")
} else if y <= 1 {
return y
}
x0 := y / 2
x1 := (x0 + y/x0) / 2
for x1 < x0 {
x0 = x1
x1 = (x0 + y/x0) / 2
}
return x0
}