mirror of
https://github.com/tuneinsight/lattigo.git
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69 lines
1.7 KiB
Go
69 lines
1.7 KiB
Go
// Package utils implements various helper functions.
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package utils
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import (
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"math/bits"
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"reflect"
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"golang.org/x/exp/constraints"
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)
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// Min returns the minimum value of the two inputs.
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func Min[V constraints.Ordered](a, b V) (r V) {
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if a <= b {
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return a
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}
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return b
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}
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// Max returns the maximum value of the two inputs.
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func Max[V constraints.Ordered](a, b V) (r V) {
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if a >= b {
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return a
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}
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return b
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}
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// IsNil returns true either type or value are nil.
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// Only interfaces or pointers to objects should be passed as argument.
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func IsNil(i interface{}) bool {
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return i == nil || reflect.ValueOf(i).IsNil()
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}
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// BitReverse64 returns the bit-reverse value of the input value, within a context of 2^bitLen.
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func BitReverse64[V uint64 | uint32 | int | int64](index V, bitLen int) uint64 {
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return bits.Reverse64(uint64(index)) >> (64 - bitLen)
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}
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// HammingWeight64 returns the hamming weight if the input value.
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func HammingWeight64[V uint64 | uint32 | int | int64](x V) V {
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y := uint64(x)
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y -= (y >> 1) & 0x5555555555555555
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y = (y & 0x3333333333333333) + ((y >> 2) & 0x3333333333333333)
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y = (y + (y >> 4)) & 0x0f0f0f0f0f0f0f0f
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return V(((y * 0x0101010101010101) & 0xffffffffffffffff) >> 56)
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}
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// AllDistinct returns true if all elements in s are distinct, and false otherwise.
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func AllDistinct[V comparable](s []V) bool {
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m := make(map[V]struct{}, len(s))
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for _, si := range s {
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if _, exists := m[si]; exists {
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return false
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}
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m[si] = struct{}{}
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}
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return true
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}
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// GCD computes the greatest common divisor between a and b.
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func GCD[V uint64 | uint32 | int | int64](a, b V) V {
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if a == 0 || b == 0 {
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return 0
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}
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for b != 0 {
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a, b = b, a%b
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}
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return a
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}
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