From 3489c9f131ef1d19040c3367bd926d7737604dab Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Wed, 6 May 2026 21:14:49 +0000
Subject: [PATCH] =?UTF-8?q?apl:=20each=20f=C2=A8=20monadic=20+=20dyadic=20?=
 =?UTF-8?q?(+14=20tests,=20139/139)?=
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---
 lib/apl/runtime.sx         | 35 +++++++++++++++
 lib/apl/tests/operators.sx | 89 +++++++++++++++++++++++++++++++++++++-
 plans/apl-on-sx.md         |  3 +-
 3 files changed, 125 insertions(+), 2 deletions(-)

diff --git a/lib/apl/runtime.sx b/lib/apl/runtime.sx
index ea252013..e26dcf1f 100644
--- a/lib/apl/runtime.sx
+++ b/lib/apl/runtime.sx
@@ -961,3 +961,38 @@
                           (rest col))))
                     (range 0 inner-size)))
                 (range 0 first-dim)))))))))
+
+(define
+  apl-each
+  (fn
+    (f arr)
+    (let
+      ((shape (get arr :shape)) (ravel (get arr :ravel)))
+      (make-array
+        shape
+        (map (fn (x) (disclose (f (apl-scalar x)))) ravel)))))
+
+(define
+  apl-each-dyadic
+  (fn
+    (f a b)
+    (cond
+      ((and (scalar? a) (scalar? b)) (apl-scalar (disclose (f a b))))
+      ((scalar? a)
+        (make-array
+          (get b :shape)
+          (map (fn (x) (disclose (f a (apl-scalar x)))) (get b :ravel))))
+      ((scalar? b)
+        (make-array
+          (get a :shape)
+          (map (fn (x) (disclose (f (apl-scalar x) b))) (get a :ravel))))
+      (else
+        (if
+          (equal? (get a :shape) (get b :shape))
+          (make-array
+            (get a :shape)
+            (map
+              (fn (x y) (disclose (f (apl-scalar x) (apl-scalar y))))
+              (get a :ravel)
+              (get b :ravel)))
+          (error "length error: shape mismatch"))))))
diff --git a/lib/apl/tests/operators.sx b/lib/apl/tests/operators.sx
index 8b2be5cc..9c17911b 100644
--- a/lib/apl/tests/operators.sx
+++ b/lib/apl/tests/operators.sx
@@ -157,4 +157,91 @@
 (apl-test
   "scan-first max\\ matrix col-wise running max"
   (rv (apl-scan-first apl-max (make-array (list 3 2) (list 3 1 4 1 5 9))))
-  (list 3 1 4 1 5 9))
\ No newline at end of file
+  (list 3 1 4 1 5 9))
+
+(apl-test
+  "each negate vector"
+  (rv (apl-each apl-neg-m (make-array (list 3) (list 1 2 3))))
+  (list -1 -2 -3))
+
+(apl-test
+  "each negate vector preserves shape"
+  (sh (apl-each apl-neg-m (make-array (list 3) (list 1 2 3))))
+  (list 3))
+
+(apl-test
+  "each reciprocal vector"
+  (rv (apl-each apl-recip (make-array (list 3) (list 1 2 4))))
+  (list 1 (/ 1 2) (/ 1 4)))
+
+(apl-test
+  "each abs vector"
+  (rv (apl-each apl-abs (make-array (list 4) (list -1 2 -3 4))))
+  (list 1 2 3 4))
+
+(apl-test "each scalar" (rv (apl-each apl-neg-m (apl-scalar 5))) (list -5))
+
+(apl-test
+  "each scalar shape"
+  (sh (apl-each apl-neg-m (apl-scalar 5)))
+  (list))
+
+(apl-test
+  "each negate matrix shape"
+  (sh (apl-each apl-neg-m (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 2 3))
+
+(apl-test
+  "each negate matrix values"
+  (rv (apl-each apl-neg-m (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list -1 -2 -3 -4 -5 -6))
+
+(apl-test
+  "each-dyadic scalar+scalar"
+  (rv (apl-each-dyadic apl-add (apl-scalar 3) (apl-scalar 4)))
+  (list 7))
+
+(apl-test
+  "each-dyadic scalar+vector"
+  (rv
+    (apl-each-dyadic
+      apl-add
+      (apl-scalar 10)
+      (make-array (list 3) (list 1 2 3))))
+  (list 11 12 13))
+
+(apl-test
+  "each-dyadic vector+scalar"
+  (rv
+    (apl-each-dyadic
+      apl-add
+      (make-array (list 3) (list 1 2 3))
+      (apl-scalar 10)))
+  (list 11 12 13))
+
+(apl-test
+  "each-dyadic vector+vector"
+  (rv
+    (apl-each-dyadic
+      apl-add
+      (make-array (list 3) (list 1 2 3))
+      (make-array (list 3) (list 10 20 30))))
+  (list 11 22 33))
+
+(apl-test
+  "each-dyadic mul matrix+matrix shape"
+  (sh
+    (apl-each-dyadic
+      apl-mul
+      (make-array (list 2 2) (list 1 2 3 4))
+      (make-array (list 2 2) (list 5 6 7 8))))
+  (list 2 2))
+
+(apl-test
+  "each-dyadic mul matrix+matrix values"
+  (rv
+    (apl-each-dyadic
+      apl-mul
+      (make-array (list 2 2) (list 1 2 3 4))
+      (make-array (list 2 2) (list 5 6 7 8))))
+  (list 5 12 21 32))
\ No newline at end of file
diff --git a/plans/apl-on-sx.md b/plans/apl-on-sx.md
index 8920b8c5..1140acef 100644
--- a/plans/apl-on-sx.md
+++ b/plans/apl-on-sx.md
@@ -75,7 +75,7 @@ Core mapping:
 ### Phase 4 — operators (THE SHOWCASE)
 - [x] Reduce `f/` (last axis), `f⌿` (first axis) — including `∧/`, `∨/`, `+/`, `×/`, `⌈/`, `⌊/`
 - [x] Scan `f\`, `f⍀`
-- [ ] Each `f¨` — applies `f` to each scalar/element
+- [x] Each `f¨` — applies `f` to each scalar/element
 - [ ] Outer product `∘.f` — `1 2 3 ∘.× 1 2 3` ↦ multiplication table
 - [ ] Inner product `f.g` — `+.×` is matrix multiply
 - [ ] Commute `f⍨` — `f⍨ x` ↔ `x f x`, `x f⍨ y` ↔ `y f x`
@@ -118,6 +118,7 @@ data; format for string templating.
 
 _Newest first._
 
+- 2026-05-06: Phase 4 step 3 — each f¨ (monadic apl-each + dyadic apl-each-dyadic); scalar broadcast both sides; 139/139 tests
 - 2026-05-06: Phase 4 step 2 — scan f\ (last axis) + f⍀ (first axis); apl-scan/apl-scan-first; 125/125 tests
 - 2026-05-06: Phase 4 step 1 — reduce f/ (last axis) + f⌿ (first axis); apl-reduce/apl-reduce-first; 110/110 tests
 - 2026-05-06: Phase 3 complete — membership ∊, dyadic ⍳ (index-of), without ~ (index-of returns nil for not-found); 94/94 tests