From 13b10e45090a5569de994847febcdf71b8f44f88 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Thu, 11 Feb 2021 13:19:52 -0500
Subject: Avoid name lookups in filter code for faster execution in current
 dzaima/BQN

---
 filter.bqn | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/filter.bqn b/filter.bqn
index effdde4..d532627 100644
--- a/filter.bqn
+++ b/filter.bqn
@@ -38,19 +38,19 @@ o ← ≠◶⟨•Import∘"options.bqn", ⊑⟩ •args
 # 𝕨 is ⟨result coefficients , 𝕩 coefficients⟩.
 Filter ← {
   ⟨i0⟩‿⟨o0⟩ 𝕊𝕩:
-    b0←a0←0
-    { b0↩(o0×b0)+i0×a0↩𝕩 }¨ 𝕩
+    1↓ (×⟜o0+i0⊸×)` 0∾𝕩
  ;⟨i0,i1⟩‿⟨o0⟩ 𝕊𝕩:
-    b0←a1←a0←0
-    { b0↩(o0×b0)+(i1×a1↩𝕩)+i0×a0↩a1 }¨ 𝕩
+    b0←a1←a0←0 ⋄ coeff←∾𝕨
+    { b0↩+´coeff×⟨a0↩a1,a1↩𝕩,b0⟩ }¨ 𝕩
  ;⟨i0,i1,i2⟩‿⟨o0,o1⟩ 𝕊𝕩:
-    b1←b0←a2←a1←a0←0
-    { b1↩(o1×b0↩b1)+(o0×b0)+(i2×a2↩𝕩)+(i1×a1↩a2)+i0×a0↩a1 }¨ 𝕩
+    b1←b0←a2←a1←a0←0 ⋄ coeff←∾𝕨
+    { b1↩+´coeff×⟨a0↩a1,a1↩a2,a2↩𝕩,b0,b0↩b1⟩ }¨ 𝕩
  ;coeff 𝕊𝕩:
     a‿b ← 0×coeff  # accumulators for input and result
+    c ← ∾coeff
     {
       a«˜↩𝕩
-      r←+´coeff+´∘רa‿b
+      r←+´c×a∾b
       b«˜↩r
       r
     }¨ 𝕩
-- 
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