1 files changed, 198 insertions, 0 deletions
diff --git a/src/pkg/rand/rand.go b/src/pkg/rand/rand.go
new file mode 100644
index 000000000..2e6aab88c
--- /dev/null
+++ b/src/pkg/rand/rand.go
@@ -0,0 +1,198 @@
+// Copyright 2009 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 rand implements pseudo-random number generators.
+package rand
+
+// A Source represents a source of uniformly-distributed
+// pseudo-random int64 values in the range [0, 1<<63).
+type Source interface {
+	Int63() int64;
+	Seed(seed int64);
+}
+
+// NewSource returns a new pseudo-random Source seeded with the given value.
+func NewSource(seed int64) Source {
+	var rng rngSource;
+	rng.Seed(seed);
+	return &rng;
+}
+
+// A Rand is a source of random numbers.
+type Rand struct {
+	src Source;
+}
+
+// New returns a new Rand that uses random values from src
+// to generate other random values.
+func New(src Source) *Rand {
+	return &Rand{src};
+}
+
+// Seed uses the provided seed value to initialize the generator to a deterministic state.
+func (r *Rand) Seed(seed int64) {
+	r.src.Seed(seed);
+}
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
+func (r *Rand) Int63() int64 {
+	return r.src.Int63();
+}
+
+// Uint32 returns a pseudo-random 32-bit value as a uint32.
+func (r *Rand) Uint32() uint32 {
+	return uint32(r.Int63() >> 31);
+}
+
+// Int31 returns a non-negative pseudo-random 31-bit integer as an int32.
+func (r *Rand) Int31() int32 {
+	return int32(r.Int63() >> 32);
+}
+
+// Int returns a non-negative pseudo-random int.
+func (r *Rand) Int() int {
+	u := uint(r.Int63());
+	return int(u<<1>>1);	// clear sign bit if int == int32
+}
+
+// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n).
+func (r *Rand) Int63n(n int64) int64 {
+	if n <= 0 {
+		return 0;
+	}
+	max := int64((1<<63) - 1 - (1<<63)%uint64(n));
+	v := r.Int63();
+	for v > max {
+		v = r.Int63();
+	}
+	return v%n;
+}
+
+// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n).
+func (r *Rand) Int31n(n int32) int32 {
+	return int32(r.Int63n(int64(n)));
+}
+
+// Intn returns, as an int, a non-negative pseudo-random number in [0,n).
+func (r *Rand) Intn(n int) int {
+	return int(r.Int63n(int64(n)));
+}
+
+// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0).
+func (r *Rand) Float64() float64 {
+	return float64(r.Int63())/(1<<63);
+}
+
+// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0).
+func (r *Rand) Float32() float32 {
+	return float32(r.Float64());
+}
+
+// Float returns, as a float, a pseudo-random number in [0.0,1.0).
+func (r *Rand) Float() float {
+	return float(r.Float64());
+}
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).
+func (r *Rand) Perm(n int) []int {
+	m := make([]int, n);
+	for i := 0; i < n; i++ {
+		m[i] = i;
+	}
+	for i := 0; i < n; i++ {
+		j := r.Intn(i+1);
+		m[i], m[j] = m[j], m[i];
+	}
+	return m;
+}
+
+/*
+ * Top-level convenience functions
+ */
+
+var globalRand = New(NewSource(1))
+
+// Seed uses the provided seed value to initialize the generator to a deterministic state.
+func Seed(seed int64) {
+	globalRand.Seed(seed);
+}
+
+// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
+func Int63() int64 {
+	return globalRand.Int63();
+}
+
+// Uint32 returns a pseudo-random 32-bit value as a uint32.
+func Uint32() uint32 {
+	return globalRand.Uint32();
+}
+
+// Int31 returns a non-negative pseudo-random 31-bit integer as an int32.
+func Int31() int32 {
+	return globalRand.Int31();
+}
+
+// Int returns a non-negative pseudo-random int.
+func Int() int {
+	return globalRand.Int();
+}
+
+// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n).
+func Int63n(n int64) int64 {
+	return globalRand.Int63n(n);
+}
+
+// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n).
+func Int31n(n int32) int32 {
+	return globalRand.Int31n(n);
+}
+
+// Intn returns, as an int, a non-negative pseudo-random number in [0,n).
+func Intn(n int) int {
+	return globalRand.Intn(n);
+}
+
+// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0).
+func Float64() float64 {
+	return globalRand.Float64();
+}
+
+// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0).
+func Float32() float32 {
+	return globalRand.Float32();
+}
+
+// Float returns, as a float, a pseudo-random number in [0.0,1.0).
+func Float() float {
+	return globalRand.Float();
+}
+
+// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).
+func Perm(n int) []int {
+	return globalRand.Perm(n);
+}
+
+// NormFloat64 returns a normally distributed float64 in the range
+// [-math.MaxFloat64, +math.MaxFloat64] with
+// standard normal distribution (mean = 0, stddev = 1).
+// To produce a different normal distribution, callers can
+// adjust the output using:
+//
+//  sample = NormFloat64() * desiredStdDev + desiredMean
+//
+func NormFloat64() float64 {
+	return globalRand.NormFloat64();
+}
+
+// ExpFloat64 returns an exponentially distributed float64 in the range
+// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter
+// (lambda) is 1 and whose mean is 1/lambda (1).
+// To produce a distribution with a different rate parameter,
+// callers can adjust the output using:
+//
+//  sample = ExpFloat64() / desiredRateParameter
+//
+func ExpFloat64() float64 {
+	return globalRand.ExpFloat64();
+}