Constraints ns

src/main/clojure/clojure/core/contracts/constraints.clj

@@ -0,0 +1,76 @@
+(ns clojure.core.contracts.constraints
+  (:refer-clojure :exclude [== = not=])
+  (:use [clojure.core.contracts.impl.utils :only (defcurry-all)])
+  (:require [clojure.set  :as set]))
+
+;; # constraint functions and multimethods
+
+(def all-numbers?  #(boolean (every? number? %&)))
+(def all-positive? #(boolean (and (apply all-numbers? %&) (every? pos? %&))))
+(def all-negative? #(boolean (and (apply all-numbers? %&) (every? (complement pos?) %&))))
+(defn anything [& _] true)
+
+(defn in
+  "Takes an item and determines if it falls in the listed args.  This can be
+   used most effectively for numbers since any numbers in a vector represent
+   a range of values determined by the same arguments as given to `range`."
+  [e & args]
+  (boolean
+   (some #{e}
+         (mapcat #(if (vector? %)
+                    (apply range %)
+                    [%])
+                 args))))
+
+(def truthy #(when % true))
+(def falsey #(not (truthy %)))
+
+(defn whitelist
+  "Takes a thing with keys (i.e. maps or sets) and checks if it contains only
+   the keys listed in the given whitelist."
+  [wl things]
+  (set/subset? (set (keys things))
+               (set wl)))
+
+(defn implies
+  "Logical implication"
+  [p q]
+  (or (not p) q))
+
+(defn <-
+  "Converse implication"
+  [p q]
+  (implies q p))
+
+(defn except
+  "P except Q"
+  [p q]
+  (not (implies p q)))
+
+(defn <=>
+  "Logical equality"
+  [p q]
+  (and (implies p q)
+       (<- p q)))
+
+(defn xor
+  "Exclusive or"
+  [p q]
+    (not (<=> p q)))
+
+
+(defcurry-all clojure.core
+  == = not=)
+
+(comment
+
+  (defn sqr [n] (* n n))
+
+  (def sqr_ (with-constraints
+              sqr
+              #(not= 0 %)))
+
+  (sqr_ 100)
+  (sqr_ 0)
+)
+