1 files changed, 30 insertions, 0 deletions
diff --git a/algebraic-structures.private.list.applicative.scm b/algebraic-structures.private.list.applicative.scm
new file mode 100644
index 0000000..6bbfad7
--- /dev/null
+++ b/algebraic-structures.private.list.applicative.scm
@@ -0,0 +1,30 @@
+(module (algebraic-structures private list applicative) ()
+  (import scheme
+          (only (srfi 1) append! reverse!)
+          (only (chicken base) assert cut)
+          (only matchable match)
+          (chicken module))
+  (export pure map2)
+  (reexport (algebraic-structures list functor))
+
+  (define (pure x) (list x))
+
+  (define (rev-map f lst)
+    (let loop ((lst lst)
+               (acc '()))
+      (match lst
+        [() acc]
+        [(h . t)
+         (loop t (cons (f h) acc))])))
+
+  (define (product op lst1 lst2)
+    (let loop ((lst lst1)
+               (acc '()))
+      (match lst
+        [() (reverse! acc)]
+        [(h . t)
+         (loop t
+               (append! (rev-map (cut op h <>) lst2)
+                        acc))])))
+
+  (define map2 product))