add pred.clj, various predicates for convenience, readability

1 files changed, 103 insertions, 0 deletions

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+;;  Copyright (c) Stephen C. Gilardi. All rights reserved.
+;;  The use and distribution terms for this software are covered by the
+;;  Common Public License 1.0 (http://opensource.org/licenses/cpl.php)
+;;  which can be found in the file CPL.TXT at the root of this distribution.
+;;  By using this software in any fashion, you are agreeing to be bound by
+;;  the terms of this license.
+;;  You must not remove this notice, or any other, from this software.
+;;
+;;  pred.clj
+;;
+;;  Some clojure predicates
+;;
+;;  scgilardi (gmail)
+;;  28 June 2008
+
+(clojure/in-ns 'pred)
+(clojure/refer 'clojure)
+
+(defn coll?
+  "Returns true if x implements IPersistentCollection"
+  [x]
+  (instance? clojure.lang.IPersistentCollection x))
+
+(defn list?
+  "Returns true if x implements IPersistentList"
+  [x]
+  (instance? clojure.lang.IPersistentList x))
+
+;; map
+
+(defn set?
+  "Returns true if x implements IPersistentSet"
+  [x]
+  (instance? clojure.lang.IPersistentSet x))
+
+(defn stack?
+  "Returns true if x implements IPersistentStack"
+  [x]
+  (instance? clojure.lang.IPersistentStack x))
+
+;; vector
+
+(defn ref?
+  "Returns true if x implements IRef"
+  [x]
+  (instance? clojure.lang.IRef x))
+
+;; seq
+;; var
+
+(defn map-entry?
+  "Returns true if x is a MapEntry"
+  [x]
+  (instance? clojure.lang.MapEntry x))
+
+(defn atom?
+  "Returns true if x is not a collection"
+  [x]
+  (not (coll? x)))
+
+(defn number?
+  "Returns true if x is a Number"
+  [x]
+  (instance? Number x))
+
+(defn ratio?
+  "Returns true if x is a Ratio"
+  [x]
+  (instance? clojure.lang.Ratio x))
+
+(defn range?
+  "Returns true if x is a Range"
+  [x]
+  (instance? clojure.lang.Range x))
+
+(defn function?
+  "Returns true if x implements IFn"
+  [x]
+  (instance? clojure.lang.IFn x))
+
+(defmacro macro?
+  "Returns true if x is a function and the symbol of the
+  same name can be resolved and has its :macro metadata
+  set"
+  [x]
+  `(and (function? ~x) (boolean (:macro ^#'~x))))
+
+(defn integer?
+  "Returns true if x is even"
+  [x]
+  (or (instance? Integer x)
+      (instance? Long x)
+      (instance? BigInteger x)))
+
+(defn even?
+  "Returns true if x is even, throws an exception if x is not an integer"
+  [x]
+  (zero? (bit-and x 1)))
+
+(defn odd?
+  "Returns true if x is odd, throws an exception if x is not an integer"
+  [x]
+  (not (even? x)))