fogus

;   Copyright (c) Rich Hickey. All rights reserved.
;   The use and distribution terms for this software are covered by the
;   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;   which can be found in the file epl-v10.html 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.

(set! *warn-on-reflection* true)

fogus

(defn foo [s] (prn s))

(provide-contracts
  [foo "Only allow foo" [s] [#"foo"]])

(foo "foo")
; "foo"

(foo "bar")
; java.lang.AssertionError: Assert failed: (clojure.core/re-matches #"foo" s)

fogus

(defn cleave
  [& args]
  ((apply juxt (butlast args))
   (last args)))

(defn cleave2
  [x & fns]
  ((apply juxt fns) x))

fogus

• Clojure's Mini-languages
• clojure.rb
• Interview with Martin Odersky
• Yegge, Clojure, Arc
• Baysick

fogus

(defn symbol
  "Returns a Symbol with the given namespace and name."
  {:tag clojure.lang.Symbol
   :added "1.0"
   :changed "1.3"
   :static true}
  ([sym] (if (symbol? sym) name (clojure.lang.Symbol/intern sym)))
  ([ns sym] (clojure.lang.Symbol/intern (name ns) (name sym))))

fogus

(doseq [[fn-name fn-doc] '[[testname "sample doc"] [anothername "detailed documentation"]]]
  (eval `(defn ~fn-name ~fn-doc [a#] a#)))


(testname :foo)
;=> :foo

fogus

(defmacro gen-em [body]
  `(do 
     ~@(for [[fn-name# fn-doc#] body]
         (list 'defn fn-name# fn-doc# ['a] 'a))))

(gen-em [[foo "sample doc"] [bar "detailed documentation"]])


(foo :foo)
;=> :foo

fogus

(defn sqr [n] 
  "Squares a number"
  (* n n))

(sqr 5)
;=> 25

(alter-var-root 
  (var sqr)                     ; var to alter
  (fn [f]                       ; fn to apply to the var's value

fogus

(defn foo [] 42)

(foo)

(defn mk-foo []
  foo)

(defn mk-bar []
  (mk-foo))

fogus

(defmulti foo type)
(defmethod foo String [_]   (println "a string"))
(defmethod foo ::cereal [_] (println "some cereal"))

(foo "blah")
; a string

(foo {:a 1})
; java.lang.IllegalArgumentException: No method in multimethod 'foo' for dispatch value: class clojure.lang.PersistentArrayMap