Add !rpartial

README.md

@@ -22,6 +22,7 @@ Or you can just dump `bang.el` in your load path somewhere.
 * [!mapcat](#mapcat-fn-list) `(fn list)`
 * [!first](#first-fn-list) `(fn list)`
 * [!partial](#partial-fn-rest-args) `(fn &rest args)`
+* [!rpartial](#rpartial-fn-rest-args) `(fn &rest args)`
 * [!difference](#difference-list-list2) `(list list2)`
 * [!intersection](#intersection-list-list2) `(list list2)`
 * [!distinct](#distinct-list) `(list)`
@@ -172,14 +173,26 @@ To get the first item in the list no questions asked, use `car`.
 
 Takes a function `fn` and fewer than the normal arguments to `fn`,
 and returns a fn that takes a variable number of additional `args`.
-When called, the returned function calls `fn` with `args` +
-additional args.
+When called, the returned function calls `fn` with `args` first and
+then additional args.
 
 ```cl
-(funcall (!partial '+ 5) 3) ;; => 8
+(funcall (!partial '- 5) 3) ;; => 2
 (funcall (!partial '+ 5 2) 3) ;; => 10
 ```
 
+### !rpartial `(fn &rest args)`
+
+Takes a function `fn` and fewer than the normal arguments to `fn`,
+and returns a fn that takes a variable number of additional `args`.
+When called, the returned function calls `fn` with the additional
+args first and then `args`.
+
+```cl
+(funcall (!rpartial '- 5) 8) ;; => 3
+(funcall (!rpartial '- 5 2) 10) ;; => 3
+```
+
 ### !difference `(list list2)`
 
 Return a new list with only the members of `list` that are not in `list2`.

bang.el

@@ -141,9 +141,18 @@ Thus function FN should return a collection."
 (defun !partial (fn &rest args)
   "Takes a function FN and fewer than the normal arguments to FN,
 and returns a fn that takes a variable number of additional ARGS.
-When called, the returned function calls FN with ARGS +
-additional args."
-  (apply 'apply-partially fn args))
+When called, the returned function calls FN with ARGS first and
+then additional args."
+  `(closure (t) (&rest args)
+            (apply ',fn ,@(mapcar (lambda (arg) `',arg) args) args)))
+
+(defun !rpartial (fn &rest args)
+  "Takes a function FN and fewer than the normal arguments to FN,
+and returns a fn that takes a variable number of additional ARGS.
+When called, the returned function calls FN with the additional
+args first and then ARGS."
+  `(closure (t) (&rest args)
+            (apply ',fn (append args ',args))))
 
 (defun !distinct (list)
   "Return a new list with all duplicates removed.

examples.el

@@ -64,9 +64,13 @@
   (!!first (> it 2) '(1 2 3)) => 3)
 
 (defexamples !partial
-  (funcall (!partial '+ 5) 3) => 8
+  (funcall (!partial '- 5) 3) => 2
   (funcall (!partial '+ 5 2) 3) => 10)
 
+(defexamples !rpartial
+  (funcall (!rpartial '- 5) 8) => 3
+  (funcall (!rpartial '- 5 2) 10) => 3)
+
 (defexamples !difference
   (!difference '() '()) => '()
   (!difference '(1 2 3) '(4 5 6)) => '(1 2 3)