From 78e6b29cb7d95c2ef5984a98a4028406b0977f57 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Wed, 5 Mar 2025 20:47:24 +0100
Subject: Better primality test

---
 std/Math.bruijn | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

(limited to 'std/Math.bruijn')

diff --git a/std/Math.bruijn b/std/Math.bruijn
index 84cfae2..534afae 100644
--- a/std/Math.bruijn
+++ b/std/Math.bruijn
@@ -223,8 +223,7 @@ pascal L.iterate [L.zip-with …+… (L.{}(+0) ++ 0) (0 ; (+0))] (L.{}(+1))
 
 # characteristic prime sequence by Tromp
 characteristic-primes ki : (ki : (sieve s0)) ⧗ (List Bool)
-	sieve y [[k : ([(2 0) (y' 0)] (ssucc 0))]]
-		y' [[0 0] [1 (0 0)]]
+	sieve y [[k : ([(2 0) (y 0)] (ssucc 0))]]
 		ssucc [[[[1 : (0 (3 2))]]]]
 	s0 [[[ki : (0 2)]]]
 
@@ -237,6 +236,12 @@ primes* L.nub ((…≠?… (+1)) ∘∘ gcd) (L.iterate ++‣ (+2)) ⧗ (List Nu
 # primality test
 prime? L.index characteristic-primes ⧗ Number → Boolean
 
+:test (prime? (+2)) ([[1]])
+:test (prime? (+3)) ([[1]])
+:test (prime? (+4)) ([[0]])
+:test (prime? (+5)) ([[1]])
+:test (prime? (+6)) ([[0]])
+
 # prime factors
 factors \divs primes ⧗ Number → (List Number)
 	divs y [[&[[&[[3 ⋅ 3 >? 4 case-1 (=?0 case-2 case-3)]] (quot-rem 2 1)]]]]
-- 
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