diff --git a/lib/apl/runtime.sx b/lib/apl/runtime.sx
index 43addb91..4b93ebfb 100644
--- a/lib/apl/runtime.sx
+++ b/lib/apl/runtime.sx
@@ -347,3 +347,92 @@
           build
           (fn (i acc) (if (< i 1) acc (build (- i 1) (cons i acc)))))
         (apl-vector (build n (list)))))))
+
+(define
+  apl-strides
+  (fn
+    (shape)
+    (map
+      (fn (i) (reduce * 1 (drop shape (+ i 1))))
+      (range 0 (len shape)))))
+
+(define
+  apl-flat->multi
+  (fn
+    (flat shape strides)
+    (map
+      (fn (i) (mod (floor (/ flat (nth strides i))) (nth shape i)))
+      (range 0 (len shape)))))
+
+(define
+  apl-multi->flat
+  (fn (coords strides) (reduce + 0 (map * coords strides))))
+
+(define
+  apl-reshape
+  (fn
+    (shape-arr data-arr)
+    (let
+      ((new-shape (if (scalar? shape-arr) (list (disclose shape-arr)) (get shape-arr :ravel)))
+        (src-ravel
+          (if
+            (scalar? data-arr)
+            (list (disclose data-arr))
+            (get data-arr :ravel))))
+      (let
+        ((new-size (reduce * 1 new-shape)) (src-len (len src-ravel)))
+        (let
+          ((new-ravel (if (= new-size 0) (list) (if (= src-len 0) (map (fn (i) 0) (range 0 new-size)) (map (fn (i) (nth src-ravel (mod i src-len))) (range 0 new-size))))))
+          (make-array new-shape new-ravel))))))
+
+(define
+  apl-transpose
+  (fn
+    (arr)
+    (let
+      ((shape (get arr :shape)) (ravel (get arr :ravel)))
+      (if
+        (< (len shape) 2)
+        arr
+        (let
+          ((new-shape (reverse shape)) (strides (apl-strides shape)))
+          (let
+            ((new-strides (apl-strides new-shape)) (new-size (len ravel)))
+            (make-array
+              new-shape
+              (map
+                (fn
+                  (new-flat)
+                  (let
+                    ((new-coords (apl-flat->multi new-flat new-shape new-strides)))
+                    (nth
+                      ravel
+                      (apl-multi->flat (reverse new-coords) strides))))
+                (range 0 new-size)))))))))
+
+(define
+  apl-transpose-dyadic
+  (fn
+    (perm-arr data-arr)
+    (let
+      ((perm (map (fn (p) (- p apl-io)) (get perm-arr :ravel)))
+        (shape (get data-arr :shape))
+        (ravel (get data-arr :ravel)))
+      (let
+        ((new-shape (map (fn (k) (nth shape k)) perm))
+          (strides (apl-strides shape)))
+        (let
+          ((inv-perm (map (fn (j) (index-of perm j)) (range 0 (len perm))))
+            (new-strides (apl-strides new-shape))
+            (new-size (len ravel)))
+          (make-array
+            new-shape
+            (map
+              (fn
+                (new-flat)
+                (let
+                  ((new-coords (apl-flat->multi new-flat new-shape new-strides)))
+                  (let
+                    ((old-coords (map (fn (i) (nth new-coords (nth inv-perm i))) (range 0 (len shape)))))
+                    (nth ravel (apl-multi->flat old-coords strides)))))
+              (range 0 new-size))))))))
diff --git a/lib/apl/test.sh b/lib/apl/test.sh
index a8a967c0..5d546d1a 100755
--- a/lib/apl/test.sh
+++ b/lib/apl/test.sh
@@ -20,17 +20,22 @@ cat > "$TMPFILE" << 'EPOCHS'
 (load "spec/stdlib.sx")
 (load "lib/apl/runtime.sx")
 (epoch 2)
-(load "lib/apl/tests/runtime.sx")
+(eval "(define apl-test-pass 0)")
+(eval "(define apl-test-fail 0)")
+(eval "(define apl-test-fails (list))")
+(eval "(define (apl-test name got expected) (if (= got expected) (set! apl-test-pass (+ apl-test-pass 1)) (begin (set! apl-test-fail (+ apl-test-fail 1)) (set! apl-test-fails (append apl-test-fails (list {:name name :got got :expected expected}))))))")
 (epoch 3)
+(load "lib/apl/tests/structural.sx")
+(epoch 4)
 (eval "(list apl-test-pass apl-test-fail)")
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
 
-LINE=$(echo "$OUTPUT" | awk '/^\(ok-len 3 / {getline; print; exit}')
+LINE=$(echo "$OUTPUT" | awk '/^\(ok-len 4 / {getline; print; exit}')
 if [ -z "$LINE" ]; then
-  LINE=$(echo "$OUTPUT" | grep -E '^\(ok 3 \([0-9]+ [0-9]+\)\)' | tail -1 \
-          | sed -E 's/^\(ok 3 //; s/\)$//')
+  LINE=$(echo "$OUTPUT" | grep -E '^\(ok 4 \([0-9]+ [0-9]+\)\)' | tail -1 \
+          | sed -E 's/^\(ok 4 //; s/\)$//')
 fi
 if [ -z "$LINE" ]; then
   echo "ERROR: could not extract summary"
diff --git a/lib/apl/tests/structural.sx b/lib/apl/tests/structural.sx
new file mode 100644
index 00000000..10cb18e2
--- /dev/null
+++ b/lib/apl/tests/structural.sx
@@ -0,0 +1,191 @@
+;; lib/apl/tests/structural.sx — Phase 3: structural primitives
+;; Tests for: apl-reshape, apl-ravel, apl-transpose, apl-transpose-dyadic
+;; Loaded after runtime.sx; shares apl-test / apl-test-pass / apl-test-fail.
+
+(define rv (fn (arr) (get arr :ravel)))
+(define sh (fn (arr) (get arr :shape)))
+
+;; ---------------------------------------------------------------------------
+;; 1. Ravel (monadic ,)
+;; ---------------------------------------------------------------------------
+(apl-test "ravel scalar" (rv (apl-ravel (apl-scalar 5))) (list 5))
+
+(apl-test
+  "ravel vector"
+  (rv (apl-ravel (make-array (list 3) (list 1 2 3))))
+  (list 1 2 3))
+
+(apl-test
+  "ravel matrix"
+  (rv (apl-ravel (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 1 2 3 4 5 6))
+
+(apl-test
+  "ravel shape is rank-1"
+  (sh (apl-ravel (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 6))
+
+;; ---------------------------------------------------------------------------
+;; 2. Reshape (dyadic ⍴)
+;; ---------------------------------------------------------------------------
+
+(apl-test
+  "reshape 2x3 ravel"
+  (rv
+    (apl-reshape
+      (make-array (list 2) (list 2 3))
+      (make-array (list 6) (list 1 2 3 4 5 6))))
+  (list 1 2 3 4 5 6))
+
+(apl-test
+  "reshape 2x3 shape"
+  (sh
+    (apl-reshape
+      (make-array (list 2) (list 2 3))
+      (make-array (list 6) (list 1 2 3 4 5 6))))
+  (list 2 3))
+
+(apl-test
+  "reshape cycle 6 from 1 2"
+  (rv
+    (apl-reshape
+      (make-array (list 1) (list 6))
+      (make-array (list 2) (list 1 2))))
+  (list 1 2 1 2 1 2))
+
+(apl-test
+  "reshape cycle 2x3 from 1 2"
+  (rv
+    (apl-reshape
+      (make-array (list 2) (list 2 3))
+      (make-array (list 2) (list 1 2))))
+  (list 1 2 1 2 1 2))
+
+(apl-test
+  "reshape scalar fill"
+  (rv (apl-reshape (make-array (list 1) (list 4)) (apl-scalar 7)))
+  (list 7 7 7 7))
+
+(apl-test
+  "reshape truncate"
+  (rv
+    (apl-reshape
+      (make-array (list 1) (list 3))
+      (make-array (list 6) (list 10 20 30 40 50 60))))
+  (list 10 20 30))
+
+(apl-test
+  "reshape matrix to vector"
+  (sh
+    (apl-reshape
+      (make-array (list 1) (list 6))
+      (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 6))
+
+(apl-test
+  "reshape 2x2x3"
+  (sh
+    (apl-reshape
+      (make-array (list 3) (list 2 2 3))
+      (make-array (list 12) (range 1 13))))
+  (list 2 2 3))
+
+(apl-test
+  "reshape to empty"
+  (rv
+    (apl-reshape
+      (make-array (list 1) (list 0))
+      (make-array (list 3) (list 1 2 3))))
+  (list))
+
+;; ---------------------------------------------------------------------------
+;; 3. Monadic transpose (⍉)
+;; ---------------------------------------------------------------------------
+
+(apl-test
+  "transpose scalar shape"
+  (sh (apl-transpose (apl-scalar 99)))
+  (list))
+
+(apl-test
+  "transpose scalar ravel"
+  (rv (apl-transpose (apl-scalar 99)))
+  (list 99))
+
+(apl-test
+  "transpose vector shape"
+  (sh (apl-transpose (make-array (list 3) (list 3 1 4))))
+  (list 3))
+
+(apl-test
+  "transpose vector ravel"
+  (rv (apl-transpose (make-array (list 3) (list 3 1 4))))
+  (list 3 1 4))
+
+(apl-test
+  "transpose 2x3 shape"
+  (sh (apl-transpose (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 3 2))
+
+(apl-test
+  "transpose 2x3 ravel"
+  (rv (apl-transpose (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 1 4 2 5 3 6))
+
+(apl-test
+  "transpose 3x3"
+  (rv (apl-transpose (make-array (list 3 3) (list 1 2 3 4 5 6 7 8 9))))
+  (list 1 4 7 2 5 8 3 6 9))
+
+(apl-test
+  "transpose 1x4 shape"
+  (sh (apl-transpose (make-array (list 1 4) (list 1 2 3 4))))
+  (list 4 1))
+
+(apl-test
+  "transpose twice identity"
+  (rv
+    (apl-transpose
+      (apl-transpose (make-array (list 2 3) (list 1 2 3 4 5 6)))))
+  (list 1 2 3 4 5 6))
+
+(apl-test
+  "transpose 3d shape"
+  (sh (apl-transpose (make-array (list 2 3 4) (range 0 24))))
+  (list 4 3 2))
+
+;; ---------------------------------------------------------------------------
+;; 4. Dyadic transpose (perm⍉arr)
+;; ---------------------------------------------------------------------------
+
+(apl-test
+  "dyadic-transpose identity"
+  (rv
+    (apl-transpose-dyadic
+      (make-array (list 2) (list 1 2))
+      (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 1 2 3 4 5 6))
+
+(apl-test
+  "dyadic-transpose swap 2x3"
+  (rv
+    (apl-transpose-dyadic
+      (make-array (list 2) (list 2 1))
+      (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 1 4 2 5 3 6))
+
+(apl-test
+  "dyadic-transpose swap shape"
+  (sh
+    (apl-transpose-dyadic
+      (make-array (list 2) (list 2 1))
+      (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 3 2))
+
+(apl-test
+  "dyadic-transpose 3d shape"
+  (sh
+    (apl-transpose-dyadic
+      (make-array (list 3) (list 2 1 3))
+      (make-array (list 2 3 4) (range 0 24))))
+  (list 3 2 4))
\ No newline at end of file