Use an RNG parameter for array:random(), array:shuffle(),

array:shuffled()

1 files changed, 25 insertions, 0 deletions

diff --git a/test/arrays.tm b/test/arrays.tm
index e1c31cf6..25d45582 100644
--- a/test/arrays.tm
+++ b/test/arrays.tm
@@ -173,3 +173,28 @@ func main():
 	>> [4, 5, 6]:first(func(i:&Int): i:is_prime())
 	= 2?
 
+	test_seeded_rng()
+
+# Inspired by: https://nullprogram.com/blog/2017/09/21/
+struct RNGxoroshiro128(s0=Int64.random(),s1=Int64.random()):
+	func int_fn(rng:@RNGxoroshiro128 -> func(->Int64)):
+		return func(-> Int64):
+			s0 := rng.s0
+			s1 := rng.s1
+			result := s0:wrapping_plus(s1)
+			s1 xor= s0
+			rng.s0 = (s0 <<< 55) or (s0 >>> 9) xor s1 xor (s1 <<< 14)
+			rng.s1 = (s1 <<< 36) or (s1 >>> 28)
+			return result
+
+func test_seeded_rng():
+	!! Seeded RNG:
+	rng_state := RNGxoroshiro128(Int64.random(), Int64.random())
+	rng1 := @rng_state:int_fn()
+	rng2 := @rng_state:int_fn()
+
+	nums := [i*10 for i in 20]
+	>> nums:random(rng1) == nums:random(rng2)
+	= yes
+	>> nums:shuffled(rng1) == nums:shuffled(rng2)
+	= yes