From 2705341bb04693e388c79c106aa1f15a3a371eee Mon Sep 17 00:00:00 2001
From: Edward Langley <el-github@elangley.org>
Date: Sat, 15 Jul 2023 10:22:38 -0700
Subject: [PATCH] feat: add transform

---
 lens.lisp    |  7 +++++++
 package.lisp |  2 +-
 t/lens.lisp  | 11 +++++++++--
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/lens.lisp b/lens.lisp
index cf8aa7f..211cff3 100644
--- a/lens.lisp
+++ b/lens.lisp
@@ -332,6 +332,13 @@
     (apply #'concatenate result-type
            seq)))
 
+(defun transform (arg &rest args)
+  (if args
+      (lambda (fn)
+        (apply fn arg args))
+      (lambda (fn)
+        (funcall fn arg))))
+
 (defmacro calling (fun &rest args)
   (alexandria:with-gensyms (first-arg)
     `(lambda (,first-arg)
diff --git a/package.lisp b/package.lisp
index 429bc53..0d769aa 100644
--- a/package.lisp
+++ b/package.lisp
@@ -20,7 +20,7 @@
            #:maximizing #:zipping #:applying #:splice-elt
            #:transform-elt #:denest #:op #:defalias #:<> #:<>1 #:== #:•
            #:∘ #:suffixp #:functionalize #:inc #:group-by #:keys
-           #:conj #:disj #:delay #:calling))
+           #:conj #:disj #:delay #:transform))
 
 (defpackage :data-lens.transducers.internals
   (:use :cl)
diff --git a/t/lens.lisp b/t/lens.lisp
index 9109590..73e30e1 100644
--- a/t/lens.lisp
+++ b/t/lens.lisp
@@ -275,5 +275,12 @@
                            (vector 0 1 2))))
   (5am:is (equal "Abc"
                  (funcall (data-lens:transform-elt 0 'char-upcase)
-                          "abc")))
-  )
+                          "abc"))))
+
+(5am:def-test transform (:suite :data-lens.lens :depends-on (and functionalize))
+  (5am:is (equal (funcall (data-lens:transform 1) #'1+)
+                 2))
+
+  (5am:is (equal (funcall (data-lens:transform 1)
+                          (data-lens:juxt '1- 'identity '1+))
+                 '(0 1 2))))