From feeb63e7c4bc7a608f513ff350094d7f9b93e497 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Sat, 11 Dec 2021 08:18:00 -0500
Subject: Fix up the prime sieve

---
 examples/fifty.bqn | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

(limited to 'examples')

diff --git a/examples/fifty.bqn b/examples/fifty.bqn
index c514ad7d..1b31814e 100644
--- a/examples/fifty.bqn
+++ b/examples/fifty.bqn
@@ -226,21 +226,23 @@ CRT ← {
 ! 2‿¯1‿1 ≡ 4 XEA 6
 ! 12‿9 ≡ 4‿1 CRT 6‿3
 
-# 46 (not working yet)
+# 46
 Sieve←{
   4≥𝕩 ? 𝕩⥊0‿0‿1‿1;
   𝕊 n:
   r←⌊√n
   p ← 2‿3‿5‿7‿11‿13‿17‿19‿23‿29‿31‿37‿41‿43
-  p ↩ •Show (1+⊑(n≤×`p)⊐⥊1)↑p
-  b ← 0⌾(0⊸⊑)⋈ {(m⥊𝕩)>m⥊𝕨↑1 ⊣ m←n⌊𝕨×≢𝕩}´ ⌽1∾p
+  p ↩ (1+(×`p)⊸⍋⌾<n-1)↑p
+  b ← 0⌾(1⊸⊑) 1 {m←n⌊𝕨×≠𝕩 ⋄ (m⥊𝕩)>m⥊𝕨↑1}´ ⌽p
   {
-    r<⊑b⊐⥊1 ? b⊣b ↩ 1⌾(𝕩⊸⊑)b;
-    q←⊑b⊐⥊1
-    b ↩ 0⌾((q∾q×/b↑˜⌈n÷q)⊸⊑) b
+    r≥q←b⊸⊐⌾<1 ?
+    b 0¨⌾((q∾q×/b↑˜⌈n÷q)⊸⊏)↩
     𝕊 𝕩∾q
+  ;
+    b 1¨⌾(𝕩⊸⊏)↩
   }p
 }
+! 2‿3‿5‿7‿11‿13‿17‿19‿23‿29 ≡ /Sieve 30
 
 # 47
 Pg ← •rand.Deal{
-- 
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