@@ -1,8 +1,10 @@ +; Chapter 5, entitled "Returning Functions", is where we really start to see the power of functional programming. It is the types of problems outlined in the chapter where [Clojure](http://clojure.org) really shines. In fact, many of the functions created by Paul Graham in *On Lisp* are built into Clojure, as I will show below. + ; As always, I will post when the code is "complete", but my progress can be followed on [Github](http://github.com/fogus/polyglot/tree/master/reading/onlisp). Also, this post is executable, just copy and paste into a Clojure REPL. ; pg. 62 -; Clojure does not have a typecase function, but one could be made fairly easily by writing a macro that expands into something like: +; Clojure does not have a typecase function, but one could be made by writing a macro that expands into something like (I stress 'like' as this is not exactly correct): ;<pre lang="lisp"> (defn joiner [obj] @@ -13,7 +15,7 @@ ;</pre> -; Clojure of courser has a multi-method facility that would provide something similar ala: +; Clojure of courser has a multi-method facility that would provide something similar: ;<pre lang="lisp"> (defmulti joiner class) @@ -27,7 +29,7 @@ (joiner "test") ;</pre> -; Of course it would be nice if we could use type hints for dispatch and simplify the API. I will not hold my breath for this (especially since it breaks CLojure's current intent for type hints). +; Of course it would be nice if we could use type hints for dispatch and simplify the API. I will not hold my breath for this (especially since it breaks Clojure's current intent for type hints... and my comment on it was ignored :p). ;<pre lang="lisp"> (defn foo @@ -38,7 +40,7 @@ ; pg. 63 -; One of PG's famous "inventions" is the make-adder function. He originally presented it as a test for programming language X which is used to determine how such a simple function cannot be easily defined in many (at the time) popular languages. Of course, since Clojure has closures like Lisp, it's a no-brainer. +; One of PG's famous "inventions" is the make-adder function. He [originally presented it](http://www.paulgraham.com/icad.html) as a test for programming language X which is used to determine how such a simple function cannot be easily defined in many (at the time) popular languages. Of course, since Clojure has closures like Lisp, it's a no-brainer. ;<pre lang="lisp"> (defn make-adder [n] @@ -69,10 +71,6 @@ ;<pre lang="lisp"> (defn memoize - "Returns a memoized version of a referentially transparent function. The - memoized version of the function keeps a cache of the mapping from arguments - to results and, when calls with the same arguments are repeated often, has - higher performance at the expense of higher memory use." [function] (let [cache (ref {})] (fn [& args] reading/onlisp/chapter5.clj e14c39279457a4149486b04ef6af77e4ab6356b7 Fogus devnull@earthvssoup.com http://github.com/fogus/polyglot/commit/4de0344dc8743e68b8391fd21f19cfc436b9d8a3 4de0344dc8743e68b8391fd21f19cfc436b9d8a3 2008-10-24T10:40:12-07:00 2008-10-24T10:40:12-07:00 1st pub version f6d3f044773a5d38d3c596c13f0a0a0a0f4161c8 Fogus devnull@earthvssoup.com