From 2a7fbdc507e620d8de82d497d7ba0180b1a494c5 Mon Sep 17 00:00:00 2001
From: Fuco1 <dota.keys@gmail.com>
Date: Fri, 16 Aug 2013 18:41:27 +0200
Subject: [PATCH] Update -max-by & friends

---
 README.md       | 56 ++++++++++++++++++++++-----------------
 dash.el         | 70 ++++++++++++++++++++++---------------------------
 dev/examples.el | 28 ++++++++++----------
 3 files changed, 78 insertions(+), 76 deletions(-)

diff --git a/README.md b/README.md
index 6261ac6..a0cab04 100644
--- a/README.md
+++ b/README.md
@@ -29,10 +29,10 @@ Or you can just dump `dash.el` in your load path somewhere.
 * [-count](#-count-pred-list) `(pred list)`
 * [-sum](#-sum-list) `(list)`
 * [-product](#-product-list) `(list)`
-* [-min](#-min-x-rest-xs) `(x &rest xs)`
-* [-min-by](#-min-by-pred-list) `(pred list)`
-* [-max](#-max-x-rest-xs) `(x &rest xs)`
-* [-max-by](#-max-by-pred-list) `(pred list)`
+* [-min](#-min-list) `(list)`
+* [-min-by](#-min-by-comparator-list) `(comparator list)`
+* [-max](#-max-list) `(list)`
+* [-max-by](#-max-by-comparator-list) `(comparator list)`
 * [-any?](#-any-pred-list) `(pred list)`
 * [-all?](#-all-pred-list) `(pred list)`
 * [-none?](#-none-pred-list) `(pred list)`
@@ -329,44 +329,52 @@ Return the product of `list`.
 (-product '(1 2 3)) ;; => 6
 ```
 
-### -min `(x &rest xs)`
+### -min `(list)`
 
-Return the smallest value of all arguments.
+Return the smallest value from `list` of numbers or markers.
 
 ```cl
-(-min 0) ;; => 0
-(-min 1) ;; => 1
-(-min 1 2 3) ;; => 1
+(-min '(0)) ;; => 0
+(-min '(3 2 1)) ;; => 1
+(-min '(1 2 3)) ;; => 1
 ```
 
-### -min-by `(pred list)`
+### -min-by `(comparator list)`
 
-Call `pred` for each item in `list` and return item with smallest value.
+Take a comparison function `comparator` and a `list` and return
+the least element of the list by the comparison function.
+
+See also combinator `-on` which can transform the values before
+comparing them.
 
 ```cl
-(-min-by 'identity '()) ;; => nil
-(-min-by 'identity '(1)) ;; => 1
-(--min-by (cdr it) '((a . 1) (b . 2) (c . 3))) ;; => '(a . 1)
+(-min-by '> '(4 3 6 1)) ;; => 1
+(-min-by (-on '> 'length) '((1 2 3) (1) (1 2))) ;; => '(1)
+(-min-by (-on 'string-lessp 'int-to-string) '(2 100 22)) ;; => 22
 ```
 
-### -max `(x &rest xs)`
+### -max `(list)`
 
-Return the largest value of all arguments.
+Return the largest value from `list` of numbers or markers.
 
 ```cl
-(-max 0) ;; => 0
-(-max 1) ;; => 1
-(-max 1 2 3) ;; => 3
+(-max '(0)) ;; => 0
+(-max '(3 2 1)) ;; => 3
+(-max '(1 2 3)) ;; => 3
 ```
 
-### -max-by `(pred list)`
+### -max-by `(comparator list)`
+
+Take a comparison function `comparator` and a `list` and return
+the greatest element of the list by the comparison function.
 
-Call `pred` for each item in `list` and return item with largest value.
+See also combinator `-on` which can transform the values before
+comparing them.
 
 ```cl
-(-max-by 'identity '()) ;; => nil
-(-max-by 'identity '(1)) ;; => 1
-(--max-by (cdr it) '((a . 1) (b . 2) (c . 3))) ;; => '(c . 3)
+(-max-by '> '(4 3 6 1)) ;; => 6
+(-max-by (-on '> 'car) '((2 2 3) (3) (1 2))) ;; => '(3)
+(-max-by (-on '> 'string-to-int) '("1" "2" "3")) ;; => "3"
 ```
 
 ### -any? `(pred list)`
diff --git a/dash.el b/dash.el
index 51802bb..e70736d 100644
--- a/dash.el
+++ b/dash.el
@@ -906,47 +906,41 @@ Returns nil if N is less than 1."
   "Return the product of LIST."
   (apply '* list))
 
-(defun -min (x &rest xs)
-  "Return the smallest value of all arguments."
-  (apply 'min (cons x xs)))
-
-(defun -min-by (pred list)
-  "Call PRED for each item in LIST and return item with smallest value."
-  (let (min-item (min-value most-positive-fixnum))
-    (-each
-     list
-     (lambda (item)
-       (let ((item-value (funcall pred item)))
-         (when (< item-value min-value)
-           (setq min-value item-value)
-           (setq min-item item)))))
-    min-item))
+(defun -max (list)
+  "Return the largest value from LIST of numbers or markers."
+  (apply 'max list))
 
-(defmacro --min-by (form list)
-  "Anaphoric form of `-min-by'."
-  (declare (debug t))
-  `(-min-by (lambda (it) ,form) ,list))
-
-(defun -max (x &rest xs)
-  "Return the largest value of all arguments."
-  (apply 'max (cons x xs)))
-
-(defun -max-by (pred list)
-  "Call PRED for each item in LIST and return item with largest value."
-  (let (max-item (max-value most-negative-fixnum))
-    (-each
-     list
-     (lambda (item)
-       (let ((item-value (funcall pred item)))
-         (when (> item-value max-value)
-           (setq max-value item-value)
-           (setq max-item item)))))
-    max-item))
+(defun -min (list)
+  "Return the smallest value from LIST of numbers or markers."
+  (apply 'min list))
+
+(defun -max-by (comparator list)
+  "Take a comparison function COMPARATOR and a LIST and return
+the greatest element of the list by the comparison function.
+
+See also combinator `-on' which can transform the values before
+comparing them."
+  (--reduce (if (funcall comparator it acc) it acc) list))
+
+(defun -min-by (comparator list)
+  "Take a comparison function COMPARATOR and a LIST and return
+the least element of the list by the comparison function.
+
+See also combinator `-on' which can transform the values before
+comparing them."
+  (--reduce (if (funcall comparator it acc) acc it) list))
 
 (defmacro --max-by (form list)
-  "Anaphoric form of `-max-by'."
-  (declare (debug t))
-  `(-max-by (lambda (it) ,form) ,list))
+  "Anaphoric version of `-max-by'.
+
+The items for the comparator form are exposed as \"it\" and \"other\"."
+  `(-max-by (lambda (it other) ,form) ,list))
+
+(defmacro --min-by (form list)
+  "Anaphoric version of `-min-by'.
+
+The items for the comparator form are exposed as \"it\" and \"other\"."
+  `(-min-by (lambda (it other) ,form) ,list))
 
 (eval-after-load "lisp-mode"
   '(progn
diff --git a/dev/examples.el b/dev/examples.el
index d71de97..8c750eb 100644
--- a/dev/examples.el
+++ b/dev/examples.el
@@ -110,26 +110,26 @@
   (-product '(1 2 3)) => 6)
 
 (defexamples -min
-  (-min 0) => 0
-  (-min 1) => 1
-  (-min 1 2 3) => 1)
+  (-min '(0)) => 0
+  (-min '(3 2 1)) => 1
+  (-min '(1 2 3)) => 1)
 
 (defexamples -min-by
-  (-min-by 'identity '()) => nil
-  (-min-by 'identity '(1)) => 1
-  (--min-by (cdr it) '((a . 1) (b . 2) (c . 3))) => '(a . 1)
-  (-min-by (lambda (x) (string-to-int x)) '("1" "2" "3")) => "1")
+  (-min-by '> '(4 3 6 1)) => 1
+  (-min-by (-on '> 'length) '((1 2 3) (1) (1 2))) => '(1)
+  (-min-by (-on 'string-lessp 'int-to-string) '(2 100 22)) => 22
+  (-min-by '< '(4 3 6 1)) => 6)
 
 (defexamples -max
-  (-max 0) => 0
-  (-max 1) => 1
-  (-max 1 2 3) => 3)
+  (-max '(0)) => 0
+  (-max '(3 2 1)) => 3
+  (-max '(1 2 3)) => 3)
 
 (defexamples -max-by
-  (-max-by 'identity '()) => nil
-  (-max-by 'identity '(1)) => 1
-  (--max-by (cdr it) '((a . 1) (b . 2) (c . 3))) => '(c . 3)
-  (-max-by (lambda (x) (string-to-int x)) '("1" "2" "3")) => "3")
+  (-max-by '> '(4 3 6 1)) => 6
+  (-max-by (-on '> 'car) '((2 2 3) (3) (1 2))) => '(3)
+  (-max-by (-on '> 'string-to-int) '("1" "2" "3")) => "3"
+  (-max-by '< '(4 3 6 1)) => 1)
 
 (defexamples -any?
   (-any? 'even? '(1 2 3)) => t