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Improve documentation for the mersenne module (#16824)

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* Improve documentation for mersenne

Add tests for mersenne

* Add link to Wikipedia article
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konsumlamm 2021-01-27 20:14:13 +01:00 • committed by GitHub
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2 changed files with 27 additions and 16 deletions
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32
lib/pure/mersenne.nim
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@ -7,12 +7,27 @@
# distribution, for details about the copyright. # distribution, for details about the copyright.
# #
## The [Mersenne Twister](https://en.wikipedia.org/wiki/Mersenne_Twister)
## random number generator.
##
## **Note:** The procs in this module work at compile-time.
runnableExamples:
var rand = newMersenneTwister(uint32.high) ## must be "var"
doAssert rand.getNum() != rand.getNum() ## pseudorandom number
## See also
## ========
## * `random module<random.html>`_ for Nim's standard random number generator
type type
MersenneTwister* = object MersenneTwister* = object
## The Mersenne Twister.
mt: array[0..623, uint32] mt: array[0..623, uint32]
index: int index: int
proc newMersenneTwister*(seed: uint32): MersenneTwister = proc newMersenneTwister*(seed: uint32): MersenneTwister =
## Creates a new `MersenneTwister` with seed `seed`.
result.index = 0 result.index = 0
result.mt[0] = seed result.mt[0] = seed
for i in 1'u32 .. 623'u32: for i in 1'u32 .. 623'u32:
@ -28,7 +43,7 @@ proc generateNumbers(m: var MersenneTwister) =
m.mt[i] = m.mt[i] xor 0x9908b0df'u32 m.mt[i] = m.mt[i] xor 0x9908b0df'u32
proc getNum*(m: var MersenneTwister): uint32 = proc getNum*(m: var MersenneTwister): uint32 =
## Returns the next pseudo random number ranging from 0 to high(uint32) ## Returns the next pseudorandom `uint32`.
if m.index == 0: if m.index == 0:
generateNumbers(m) generateNumbers(m)
result = m.mt[m.index] result = m.mt[m.index]
@ -38,18 +53,3 @@ proc getNum*(m: var MersenneTwister): uint32 =
result = result xor ((result shl 7'u32) and 0x9d2c5680'u32) result = result xor ((result shl 7'u32) and 0x9d2c5680'u32)
result = result xor ((result shl 15'u32) and 0xefc60000'u32) result = result xor ((result shl 15'u32) and 0xefc60000'u32)
result = result xor (result shr 18'u32) result = result xor (result shr 18'u32)
runnableExamples:
static:
block:
var rando: MersenneTwister = newMersenneTwister(uint32.high) ## Must be "var".
doAssert rando.getNum() != rando.getNum() ## Pseudo random number. Works at compile-time.
# Test
when not defined(testing) and isMainModule:
var mt = newMersenneTwister(2525)
for i in 0..99:
echo mt.getNum

11
tests/stdlib/tmersenne.nim Normal file
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@ -0,0 +1,11 @@
import std/mersenne
template main() =
var mt = newMersenneTwister(2525)
doAssert mt.getNum == 407788156'u32
doAssert mt.getNum == 1071751096'u32
doAssert mt.getNum == 3805347140'u32
static: main()
main()