Use double-bang for anaphoric functions

README.md

@@ -10,13 +10,13 @@ This is so much a work in progress that you should definitely not be using it ye
 
 ## Anaphoric functions
 
-While `!filter` takes a function to filter the list by, you can also pass
+While `!filter` takes a function to filter the list by, you can also use the
-it a form - which will then be executed with `it` exposed as the list item.
+anaphoric form with double bangs - which will then be executed with `it` exposed
-Here's an example:
+as the list item. Here's an example:
 
     (!filter (lambda (num) (= 0 (% num 2))) '(1 2 3 4)) ;; normal version
 
-    (!filter (= 0 (% it 2)) '(1 2 3 4)) ;; anaphoric version
+    (!!filter (= 0 (% it 2)) '(1 2 3 4)) ;; anaphoric version
 
 of course the original can also be written like
 

bang.el

@@ -1,4 +1,4 @@
-;;; bang.el --- A modern list library for Emacs
+;;; bang.el --- A modern list library for Emacs -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2012 Magnar Sveen, Joel McCracken
 
@@ -25,96 +25,94 @@
 
 ;;; Code:
 
-(defun !--call-with-it (form-or-fn)
+(defalias '!map 'mapcar)
-  (if (functionp form-or-fn)
+
-      (list form-or-fn 'it)
+(defmacro !!map (form list)
-    form-or-fn))
+  `(!map (lambda (it) ,form) ,list))
-
+
-(defmacro !map (form-or-fn list)
+(defun !reduce-from (fn initial-value list)
-  "Returns a new list consisting of the result of applying
+  "Returns the result of applying FN to INITIAL-VALUE and the
-FORM-OR-FN to the items in list."
+first item in LIST, then applying FN to that result and the 2nd
-  (if (functionp form-or-fn)
+item, etc. If INITIAL-VALUE contains no items, returns
-      `(mapcar #',form-or-fn ,list)
+INITIAL-VALUE and FN is not called."
-    `(mapcar #'(lambda (it) ,form-or-fn) ,list)))
+  (let ((acc initial-value))
-
+     (while list
-(defmacro !reduce-from (form-or-fn initial-value list)
+       (setq acc (funcall fn acc (car list)))
-  "Returns the result of applying FORM-OR-FN to INITIAL-VALUE and
+       (setq list (cdr list)))
-the first item in LIST, then applying FORM-OR-FN to that result
+     acc))
-and the 2nd item, etc. If INITIAL-VALUE contains no items,
+
-returns INITIAL-VALUE and FORM-OR-FN is not called."
+(defmacro !!reduce-from (form initial-value list)
-  `(let ((!--list ,list)
+  `(!reduce-from (lambda (acc it) ,form) ,initial-value ,list))
-         (!--acc ,initial-value))
+
-     (while !--list
+(defun !reduce (fn list)
-       (let ((it (car !--list))
+  "Returns the result of applying FN to the first 2 items in LIST,
-             (acc !--acc))
+then applying FN to that result and the 3rd item, etc. If LIST
-         (setq !--acc ,(if (functionp form-or-fn) (list form-or-fn 'acc 'it) form-or-fn))
+contains no items, FN must accept no arguments as well, and
-         (setq !--list (cdr !--list))))
+reduce returns the result of calling FN with no arguments. If
-     !--acc))
+LIST has only 1 item, it is returned and FN is not called."
-
+  (if list
-(defmacro !reduce (form-or-fn list)
+      (!reduce-from fn (car list) (cdr list))
-  "Returns the result of applying FORM-OR-FN to the first 2 items in LIST,
+    (funcall fn)))
-then applying FORM-OR-FN to that result and the 3rd item, etc. If
+
-LIST contains no items, FORM-OR-FN must accept no arguments as
+(defmacro !!reduce (form list)
-well, and reduce returns the result of calling FORM-OR-FN with no
+  `(!reduce (lambda (&optional acc it) ,form) ,list))
-arguments. If LIST has only 1 item, it is returned and FORM-OR-FN
+
-is not called."
+(defun !filter (fn list)
-  (if (eval list)
+  "Returns a new list of the items in LIST for which FN returns a non-nil value."
-      `(!reduce-from ,form-or-fn ,(car (eval list)) ',(cdr (eval list)))
+  (let ((result '()))
-    (if (functionp form-or-fn)
+    (while list
-        (list form-or-fn)
+      (when (funcall fn (car list))
-      `(let (acc it) ,form-or-fn))))
+        (setq result (cons (car list) result)))
-
+      (setq list (cdr list)))
-(defmacro !filter (form-or-fn list)
+    (nreverse result)))
-  "Returns a new list of the items in LIST for which FORM-OR-FN returns a non-nil value."
+
-  `(let ((!--list ,list)
+(defmacro !!filter (form list)
-         (!--result '()))
+  `(!filter (lambda (it) ,form) ,list))
-     (while !--list
+
-       (let ((it (car !--list)))
+(defun !remove (fn list)
-         (when ,(!--call-with-it form-or-fn)
+  "Returns a new list of the items in LIST for which FN returns nil."
-           (setq !--result (cons it !--result))))
+  (!!filter (not (funcall fn it)) list))
-       (setq !--list (cdr !--list)))
+
-     (nreverse !--result)))
+(defmacro !!remove (form list)
-
+  `(!!filter (not ,form) ,list))
-(defmacro !remove (form-or-fn list)
-  "Returns a new list of the items in LIST for which FORM-OR-FN returns nil."
-  `(!filter (not ,(!--call-with-it form-or-fn)) ,list))
-
-(defalias '!select '!filter)
-(defalias '!reject '!remove)
 
 (defun !concat (&rest lists)
   "Returns a new list with the concatenation of the elements in
 the supplied LISTS."
   (apply 'append (append lists '(nil))))
 
-(defmacro !partial (fn &rest args)
+(defun !mapcat (fn list)
-  "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-partially ',fn ,@args))
-
-(defmacro !mapcat (fn list)
   "Returns the result of applying concat to the result of applying map to FN and LIST.
 Thus function FN should return a collection."
-  `(apply '!concat (!map ,fn ,list)))
+  (apply '!concat (!map fn list)))
+
+(defmacro !!mapcat (form list)
+  `(!mapcat (lambda (it) ,form) ,list))
+
+(defalias '!partial 'apply-partially)
 
 (defun !uniq (list)
   "Return a new list with all duplicates removed.
 The test for equality is done with `equal',
 or with `!compare-fn' if that's non-nil."
-  (!filter (not (!contains? !--result it)) list))
+  (let ((result '()))
+    (while list
+      (when (not (!contains? result (car list)))
+        (setq result (cons (car list) result)))
+      (setq list (cdr list)))
+    (nreverse result)))
 
 (defun !intersection (list list2)
   "Return a new list containing only the elements that are members of both LIST and LIST2.
 The test for equality is done with `equal',
 or with `!compare-fn' if that's non-nil."
-  (!filter (!contains? list2 it) list))
+  (!!filter (!contains? list2 it) list))
 
 (defun !difference (list list2)
   "Return a new list with only the members of LIST that are not in LIST2.
 The test for equality is done with `equal',
 or with `!compare-fn' if that's non-nil."
-  (!filter (not (!contains? list2 it)) list))
+  (!!filter (not (!contains? list2 it)) list))
 
 (defun !contains? (list element)
   "Return whether LIST contains ELEMENT.

tests.el

@@ -7,70 +7,82 @@
 (ert-deftest map ()
   "`!map' returns a new list with the results of calling the function on each element."
   (should (equal (!map (lambda (num) (* num num)) '(1 2 3 4)) '(1 4 9 16)))
-  (should (equal (!map (* it it) '(1 2 3 4)) '(1 4 9 16)))
+  (should (equal (!map 'square '(1 2 3 4)) '(1 4 9 16)))
-  (should (equal (!map square '(1 2 3 4)) '(1 4 9 16))))
+  (should (equal (!!map (* it it) '(1 2 3 4)) '(1 4 9 16)))
+  )
 
-(ert-deftest reduce ()
+(ert-deftest reduce-from ()
-  "`!reduce' takes a list and applies the function over them to create one result"
+  "`!reduce-from' takes a list and an initial value, and applies the function over them to create one result"
-  (should (equal (!reduce + '()) 0))
+  (should (equal (!reduce '+ '()) 0))
-  (should (equal (!reduce + '(1)) 1))
+  (should (equal (!reduce '+ '(1)) 1))
-  (should (equal (!reduce + '(1 2)) 3))
+  (should (equal (!reduce '+ '(1 2)) 3))
-  (should (equal (!reduce-from + 7 '()) 7))
+  (should (equal (!reduce-from '+ 7 '()) 7))
-  (should (equal (!reduce-from + 7 '(1)) 8))
+  (should (equal (!reduce-from '+ 7 '(1)) 8))
-  (should (equal (!reduce-from + 7 '(1 2)) 10))
+  (should (equal (!reduce-from '+ 7 '(1 2)) 10))
+  (should (equal (!!reduce-from (+ acc it) 7 '(1 2 3)) 13))
+  )
 
+(ert-deftest reduce ()
+  "`!reduce' takes a list and applies the function over the elements to create one result"
   (should (equal (!reduce (lambda (memo item) (format "%s-%s" memo item)) '(1 2 3)) "1-2-3"))
-  (should (equal (!reduce (format "%s-%s" acc it) '(1 2 3)) "1-2-3"))
+  (should (equal (!!reduce (format "%s-%s" acc it) '(1 2 3)) "1-2-3"))
-  (should (equal (!reduce (format "%s-%s" acc it) '()) "nil-nil")))
+  (should (equal (!!reduce (format "%s-%s" acc it) '()) "nil-nil"))
+  )
 
 (ert-deftest filter ()
   "`!filter' returns a new list of only those elements where the predicate was non-nil."
   (should (equal (!filter (lambda (num) (= 0 (% num 2))) '(1 2 3 4)) '(2 4)))
-  (should (equal (!filter (= 0 (% it 2)) '(1 2 3 4)) '(2 4)))
+  (should (equal (!filter 'even? '(1 2 3 4)) '(2 4)))
-  (should (equal (!filter even? '(1 2 3 4)) '(2 4)))
+  (should (equal (!!filter (= 0 (% it 2)) '(1 2 3 4)) '(2 4)))
-  (should (equal (!select even? '(1 2 3 4)) '(2 4))))
+  )
 
 (ert-deftest remove ()
   "`!remove' returns a new list of only those elements where the predicate was nil."
   (should (equal (!remove (lambda (num) (= 0 (% num 2))) '(1 2 3 4)) '(1 3)))
-  (should (equal (!remove (= 0 (% it 2)) '(1 2 3 4)) '(1 3)))
+  (should (equal (!remove 'even? '(1 2 3 4)) '(1 3)))
-  (should (equal (!remove even? '(1 2 3 4)) '(1 3)))
+  (should (equal (!!remove (= 0 (% it 2)) '(1 2 3 4)) '(1 3)))
-  (should (equal (!reject even? '(1 2 3 4)) '(1 3))))
+  )
 
 (ert-deftest concat ()
   "`!concat' returns the concatenation of the elements in the supplied lists"
   (should (equal (!concat) nil))
   (should (equal (!concat '(1)) '(1)))
   (should (equal (!concat '(1) '(2)) '(1 2)))
-  (should (equal (!concat '(1) '(2 3) '(4)) '(1 2 3 4))))
+  (should (equal (!concat '(1) '(2 3) '(4)) '(1 2 3 4)))
+  )
 
 (ert-deftest mapcat ()
   "`!mapcat' applies the function to all elements of the list and then concatenates the result"
-  (should (equal (!mapcat list '(1 2 3)) '(1 2 3)))
+  (should (equal (!mapcat 'list '(1 2 3)) '(1 2 3)))
   (should (equal (!mapcat (lambda (item) (list 0 item)) '(1 2 3)) '(0 1 0 2 0 3)))
-  (should (equal (!mapcat (list 0 it) '(1 2 3)) '(0 1 0 2 0 3))))
+  (should (equal (!!mapcat (list 0 it) '(1 2 3)) '(0 1 0 2 0 3)))
+  )
 
 (ert-deftest partial ()
   "`!partial' returns a function like fn where the first arguments are filled in"
-  (should (equal (funcall (!partial + 5) 3) 8))
+  (should (equal (funcall (!partial '+ 5) 3) 8))
-  (should (equal (funcall (!partial + 5 2) 3) 10)))
+  (should (equal (funcall (!partial '+ 5 2) 3) 10))
+  )
 
 (ert-deftest difference ()
   "`!difference' returns a new list of only elements in list1 that are not in list2."
   (should (equal (!difference '() '()) '()))
   (should (equal (!difference '(1 2 3) '(4 5 6)) '(1 2 3)))
-  (should (equal (!difference '(1 2 3 4) '(3 4 5 6)) '(1 2))))
+  (should (equal (!difference '(1 2 3 4) '(3 4 5 6)) '(1 2)))
+  )
 
 (ert-deftest intersection ()
   "`!intersection' returns a new list of only elements that are in both given lists."
   (should (equal (!intersection '() '()) '()))
   (should (equal (!intersection '(1 2 3) '(4 5 6)) '()))
-  (should (equal (!intersection '(1 2 3 4) '(3 4 5 6)) '(3 4))))
+  (should (equal (!intersection '(1 2 3 4) '(3 4 5 6)) '(3 4)))
+  )
 
 (ert-deftest uniq ()
   "`!uniq' returns a new list of only unique elements."
   (should (equal (!uniq '()) '()))
-  (should (equal (!uniq '(1 2 2 4)) '(1 2 4))))
+  (should (equal (!uniq '(1 2 2 4)) '(1 2 4)))
+  )
 
 (ert-deftest contains? ()
   "`!contains?' returns t if the list contains the element."
@@ -78,4 +90,5 @@
   (should (!contains? '(1 2 3) 2))
   (should (not (!contains? '() '())))
   (should (not (!contains? '() 1)))
-  (should (not (!contains? '(1 2 4) 3))))
+  (should (not (!contains? '(1 2 4) 3)))
+  )