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rand: simplify rand.PRNG, move to optional types for error handling (#13570)
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Subhomoy Haldar
@@ -48,183 +48,6 @@ pub fn (mut rng PCG32RNG) u64() u64 {
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return u64(rng.u32()) | (u64(rng.u32()) << 32)
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}
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// u32n returns a pseudorandom 32-bit unsigned `u32` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) u32n(max u32) u32 {
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if max == 0 {
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eprintln('max must be positive')
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exit(1)
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}
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// To avoid bias, we need to make the range of the RNG a multiple of
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// max, which we do by dropping output less than a threshold.
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threshold := (-max % max)
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// Uniformity guarantees that loop below will terminate. In practice, it
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// should usually terminate quickly; on average (assuming all max's are
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// equally likely), 82.25% of the time, we can expect it to require just
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// one iteration. In practice, max's are typically small and only a
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// tiny amount of the range is eliminated.
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for {
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r := rng.u32()
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if r >= threshold {
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return r % max
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}
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}
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return u32(0)
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}
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// u64n returns a pseudorandom 64-bit unsigned `u64` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) u64n(max u64) u64 {
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if max == 0 {
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eprintln('max must be positive')
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exit(1)
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}
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threshold := (-max % max)
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for {
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r := rng.u64()
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if r >= threshold {
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return r % max
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}
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}
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return u64(0)
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}
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// u32_in_range returns a pseudorandom 32-bit unsigned `u32` in range `[min, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) u32_in_range(min u32, max u32) u32 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.u32n(u32(max - min))
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}
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// u64_in_range returns a pseudorandom 64-bit unsigned `u64` in range `[min, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) u64_in_range(min u64, max u64) u64 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.u64n(max - min)
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}
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// int returns a 32-bit signed (possibly negative) `int`.
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[inline]
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pub fn (mut rng PCG32RNG) int() int {
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return int(rng.u32())
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}
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// i64 returns a 64-bit signed (possibly negative) `i64`.
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[inline]
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pub fn (mut rng PCG32RNG) i64() i64 {
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return i64(rng.u64())
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}
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// int31 returns a 31-bit positive pseudorandom `int`.
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[inline]
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pub fn (mut rng PCG32RNG) int31() int {
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return int(rng.u32() >> 1)
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}
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// int63 returns a 63-bit positive pseudorandom `i64`.
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[inline]
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pub fn (mut rng PCG32RNG) int63() i64 {
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return i64(rng.u64() >> 1)
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}
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// intn returns a 32-bit positive `int` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) intn(max int) int {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return int(rng.u32n(u32(max)))
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}
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// i64n returns a 64-bit positive `i64` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) i64n(max i64) i64 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return i64(rng.u64n(u64(max)))
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}
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// int_in_range returns a 32-bit positive `int` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) int_in_range(min int, max int) int {
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if max <= min {
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eprintln('max must be greater than min.')
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exit(1)
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}
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return min + rng.intn(max - min)
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}
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// i64_in_range returns a 64-bit positive `i64` in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) i64_in_range(min i64, max i64) i64 {
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if max <= min {
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eprintln('max must be greater than min.')
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exit(1)
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}
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return min + rng.i64n(max - min)
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}
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// f32 returns a pseudorandom `f32` value in range `[0, 1)`.
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[inline]
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pub fn (mut rng PCG32RNG) f32() f32 {
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return f32(rng.u32()) / constants.max_u32_as_f32
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}
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// f64 returns a pseudorandom `f64` value in range `[0, 1)`.
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[inline]
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pub fn (mut rng PCG32RNG) f64() f64 {
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return f64(rng.u64()) / constants.max_u64_as_f64
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}
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// f32n returns a pseudorandom `f32` value in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) f32n(max f32) f32 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return rng.f32() * max
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}
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// f64n returns a pseudorandom `f64` value in range `[0, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) f64n(max f64) f64 {
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if max <= 0 {
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eprintln('max has to be positive.')
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exit(1)
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}
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return rng.f64() * max
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}
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// f32_in_range returns a pseudorandom `f32` in range `[min, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) f32_in_range(min f32, max f32) f32 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.f32n(max - min)
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}
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// i64_in_range returns a pseudorandom `i64` in range `[min, max)`.
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[inline]
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pub fn (mut rng PCG32RNG) f64_in_range(min f64, max f64) f64 {
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if max <= min {
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eprintln('max must be greater than min')
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exit(1)
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}
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return min + rng.f64n(max - min)
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}
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// free should be called when the generator is no longer needed
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[unsafe]
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pub fn (mut rng PCG32RNG) free() {
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