Add -zip and -zip-with

Thanks to @Fuco1 :-)
Fixes #14

README.md

@@ -45,6 +45,8 @@ Or you can just dump `dash.el` in your load path somewhere.
 * [-group-by](#-group-by-fn-list) `(fn list)`
 * [-interpose](#-interpose-sep-list) `(sep list)`
 * [-interleave](#-interleave-rest-lists) `(&rest lists)`
+* [-zip-with](#-zip-with-fn-list1-list2) `(fn list1 list2)`
+* [-zip](#-zip-list1-list2) `(list1 list2)`
 * [-first](#-first-pred-list) `(pred list)`
 * [-union](#-union-list-list2) `(list list2)`
 * [-difference](#-difference-list-list2) `(list list2)`
@@ -447,6 +449,32 @@ Returns a new list of the first item in each list, then the second etc.
 (-interleave '(1 2 3) '("a" "b")) ;; => '(1 "a" 2 "b")
 ```
 
+### -zip-with `(fn list1 list2)`
+
+Zip the two lists `list1` and `list2` using a function `fn`.  This
+function is applied pairwise taking as first argument element of
+`list1` and as second argument element of `list2` at corresponding
+position.
+
+```cl
+(-zip-with '+ '(1 2 3) '(4 5 6)) ;; => '(5 7 9)
+(-zip-with 'cons '(1 2 3) '(4 5 6)) ;; => '((1 . 4) (2 . 5) (3 . 6))
+(--zip-with (concat it " and " other) '("Batman" "Jekyll") '("Robin" "Hyde")) ;; => '("Batman and Robin" "Jekyll and Hyde")
+```
+
+### -zip `(list1 list2)`
+
+Zip the two lists together.  Return the list where elements
+are cons pairs with car being element from `list1` and cdr being
+element from `list2`.  The length of the returned list is the
+length of the shorter one.
+
+```cl
+(-zip '(1 2 3) '(4 5 6)) ;; => '((1 . 4) (2 . 5) (3 . 6))
+(-zip '(1 2 3) '(4 5 6 7)) ;; => '((1 . 4) (2 . 5) (3 . 6))
+(-zip '(1 2 3 4) '(4 5 6)) ;; => '((1 . 4) (2 . 5) (3 . 6))
+```
+
 ### -first `(pred list)`
 
 Returns the first x in `list` where (`pred` x) is non-nil, else nil.
@@ -642,7 +670,7 @@ Change `readme-template.md` or `examples-to-docs.el` instead.
 
 ## Contributors
 
- - [Fuco](https://github.com/Fuco1) contributed `-union` and `-separate`.
+ - [Matus Goljer](https://github.com/Fuco1) contributed `-union`, `-separate`, `-zip` and `-zip-with`.
  - [Takafumi Arakaki](https://github.com/tkf) contributed `-group-by`.
  - [tali713](https://github.com/tali713) is the author of `-applify`.
  - [Víctor M. Valenzuela](https://github.com/vemv) contributed `-repeat`.

dash.el

@@ -490,6 +490,46 @@ elements of LIST.  Keys are compared by `equal'."
       (setq lists (-map 'cdr lists)))
     (nreverse result)))
 
+(defmacro --separate (form list)
+  "Anaphoric form of `-separate'."
+  (let ((y (make-symbol "yes"))
+        (n (make-symbol "no")))
+    `(let (,y ,n)
+       (--each ,list (if ,form (!cons it ,y) (!cons it ,n)))
+       (list (nreverse ,y) (nreverse ,n)))))
+
+(defmacro --zip-with (form list1 list2)
+  "Anaphoric form of `-zip-with'.
+
+The elements in list1 is bound as `it`, the elements in list2 as `other`."
+  (let ((r (make-symbol "result"))
+        (l1 (make-symbol "list1"))
+        (l2 (make-symbol "list2")))
+    `(let ((,r nil)
+           (,l1 ,list1)
+           (,l2 ,list2))
+       (while (and ,l1 ,l2)
+         (let ((it (car ,l1))
+               (other (car ,l2)))
+           (!cons ,form ,r)
+           (!cdr ,l1)
+           (!cdr ,l2)))
+       (nreverse ,r))))
+
+(defun -zip-with (fn list1 list2)
+  "Zip the two lists LIST1 and LIST2 using a function FN.  This
+function is applied pairwise taking as first argument element of
+LIST1 and as second argument element of LIST2 at corresponding
+position."
+  (--zip-with (funcall fn it other) list1 list2))
+
+(defun -zip (list1 list2)
+  "Zip the two lists together.  Return the list where elements
+are cons pairs with car being element from LIST1 and cdr being
+element from LIST2.  The length of the returned list is the
+length of the shorter one."
+  (-zip-with 'cons list1 list2))
+
 (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.
@@ -682,6 +722,9 @@ Returns nil if N is less than 1."
                            "-partition-all"
                            "-interpose"
                            "-interleave"
+                           "--zip-with"
+                           "-zip-with"
+                           "-zip"
                            "--map-when"
                            "-map-when"
                            "--replace-where"
@@ -703,6 +746,7 @@ Returns nil if N is less than 1."
                                 "it"
                                 "it-index"
                                 "acc"
+                                "other"
                                 )))
        (font-lock-add-keywords 'emacs-lisp-mode `((,(concat "\\<" (regexp-opt special-variables 'paren) "\\>")
                                                    1 font-lock-variable-name-face)) 'append)

dev/examples.el

@@ -181,6 +181,16 @@
   (-interleave '(1 2 3) '("a" "b")) => '(1 "a" 2 "b")
   (-interleave '(1 2 3) '("a" "b" "c" "d")) => '(1 "a" 2 "b" 3 "c"))
 
+(defexamples -zip-with
+  (-zip-with '+ '(1 2 3) '(4 5 6)) => '(5 7 9)
+  (-zip-with 'cons '(1 2 3) '(4 5 6)) => '((1 . 4) (2 . 5) (3 . 6))
+  (--zip-with (concat it " and " other) '("Batman" "Jekyll") '("Robin" "Hyde")) => '("Batman and Robin" "Jekyll and Hyde"))
+
+(defexamples -zip
+  (-zip '(1 2 3) '(4 5 6)) => '((1 . 4) (2 . 5) (3 . 6))
+  (-zip '(1 2 3) '(4 5 6 7)) => '((1 . 4) (2 . 5) (3 . 6))
+  (-zip '(1 2 3 4) '(4 5 6)) => '((1 . 4) (2 . 5) (3 . 6)))
+
 (defexamples -first
   (-first 'even? '(1 2 3)) => 2
   (-first 'even? '(1 3 5)) => nil

readme-template.md

@@ -71,7 +71,7 @@ Change `readme-template.md` or `examples-to-docs.el` instead.
 
 ## Contributors
 
- - [Fuco](https://github.com/Fuco1) contributed `-union` and `-separate`.
+ - [Matus Goljer](https://github.com/Fuco1) contributed `-union`, `-separate`, `-zip` and `-zip-with`.
  - [Takafumi Arakaki](https://github.com/tkf) contributed `-group-by`.
  - [tali713](https://github.com/tali713) is the author of `-applify`.
  - [Víctor M. Valenzuela](https://github.com/vemv) contributed `-repeat`.