Comments for On Clojure http://onclojure.com A blog about everything Clojure Sat, 06 Mar 2010 22:25:19 +0000 http://wordpress.com/ hourly 1 Comment on Pre- and post-conditions: a quest for a nicer syntax by zahardzhan http://onclojure.com/2010/03/05/pre-and-post-conditions-a-quest-for-a-nicer-syntax/#comment-84 zahardzhan Sat, 06 Mar 2010 22:25:19 +0000 http://onclojure.com/?p=104#comment-84 "Destructuring" can be used like this, with [(automaticaly generated anonymous functions here %)] (n :is [pos? integer? (or (> 10 %) (< 5 %))] :is [neg? float?] ;; other :is act like or-clauses :is [zero? double?] :is (identical? 3 %) :is number? :type String ;; type declaration for optimization :ignore ;; like in Common Lisp :or 0) ;; when checking failed set n to 0 And, i think there must be way to write predicates without []-parens around. You may try to read some code in my post in russian - there so few lines of code. “Destructuring” can be used like this, with [(automaticaly generated anonymous functions here %)]

(n
:is [pos? integer? (or (> 10 %) (< 5 %))]
:is [neg? float?] ;; other :is act like or-clauses
:is [zero? double?]
:is (identical? 3 %)
:is number?
:type String ;; type declaration for optimization
:ignore ;; like in Common Lisp
:o r 0) ;; when checking failed set n to 0

And, i think there must be way to write predicates without []-parens around.

You may try to read some code in my post in russian – there so few lines of code.

]]> Comment on Pre- and post-conditions: a quest for a nicer syntax by khinsen http://onclojure.com/2010/03/05/pre-and-post-conditions-a-quest-for-a-nicer-syntax/#comment-83 khinsen Sat, 06 Mar 2010 17:50:32 +0000 http://onclojure.com/?p=104#comment-83 With your parenthesis-free syntax, how do you handle conditions that need parameters? As I see it, you'd have to define an anonymous literal each time. Concerning your post about function combinators, my Russian isn't quite up to it I am afraid! With your parenthesis-free syntax, how do you handle conditions that need parameters? As I see it, you’d have to define an anonymous literal each time.

Concerning your post about function combinators, my Russian isn’t quite up to it I am afraid!

]]> Comment on Pre- and post-conditions: a quest for a nicer syntax by bsteuber http://onclojure.com/2010/03/05/pre-and-post-conditions-a-quest-for-a-nicer-syntax/#comment-81 bsteuber Sat, 06 Mar 2010 09:00:18 +0000 http://onclojure.com/?p=104#comment-81 I like that =) (And I prefer the "parenthetic" version) I like that =)

(And I prefer the “parenthetic” version)

]]> Comment on Pre- and post-conditions: a quest for a nicer syntax by zahardzhan http://onclojure.com/2010/03/05/pre-and-post-conditions-a-quest-for-a-nicer-syntax/#comment-80 zahardzhan Sat, 06 Mar 2010 03:46:21 +0000 http://onclojure.com/?p=104#comment-80 Or it's better to add some sort of 'destructuring' for variables http://gist.github.com/323481 (defn (power :is number? :or #(throw 'Bad-input)) [(x :is number?) (y :is [pos? integer?]) (n :is [pos? integer?] :is [neg? float?] :is [zero? double?] :or false)] (/ x 0)) Or it’s better to add some sort of ‘destructuring’ for variables http://gist.github.com/323481

(defn (power :is number? :o r #(throw ‘Bad-input))
[(x :is number?)
(y :is [pos? integer?])
(n :is [pos? integer?] :is [neg? float?] :is [zero? double?] :o r false)]
(/ x 0))

]]> Comment on Pre- and post-conditions: a quest for a nicer syntax by zahardzhan http://onclojure.com/2010/03/05/pre-and-post-conditions-a-quest-for-a-nicer-syntax/#comment-79 zahardzhan Sat, 06 Mar 2010 03:26:46 +0000 http://onclojure.com/?p=104#comment-79 I write a post about fn/and and fn/or function combinators http://zahardzhan.posterous.com/-fnand-fnor-fnnot Pre and post conditions is full of implicit fn/and. What do you think about it? And, also, there are toooo much parenthesis in your syntax. It should be something like that: (defn power :is number? [x :is number? y :is (pos? integer?) n :is (or (pos? integer?) (neg? float?))] (apply * (repeat n x))) I write a post about fn/and and fn/or function combinators http://zahardzhan.posterous.com/-fnand-fnor-fnnot
Pre and post conditions is full of implicit fn/and. What do you think about it?

And, also, there are toooo much parenthesis in your syntax. It should be something like that:
(defn power :is number?
[x :is number?
y :is (pos? integer?)
n :is (or (pos? integer?)
(neg? float?))]
(apply * (repeat n x)))

]]> Comment on Anonymous function literals and syntax-quote don’t work well together by khinsen http://onclojure.com/2010/03/01/anonymous-function-literals-and-syntax-quote-dont-work-well-together/#comment-77 khinsen Mon, 01 Mar 2010 15:12:38 +0000 http://onclojure.com/?p=99#comment-77 When I discovered this problem, my first idea was to find a fix and propose it for inclusion in Clojure. But I didn't find any, so I wrote this post as a kind of public warning. However, Rich Hickey, Clojure's creator, did find a fix, and applied it immediately. If you work with the master branch of Clojure's github repository and pull in today's changes, the code in the example will work just fine. This may be the quickest fix of something never reported as a bug! So what's the trick? Clojure now appends <code>#</code> to the function argument symbols in expanded function literals. Syntax-quote treats such symbols specially, replacing them by guaranteed-to-be-unique generated symbols, which moreover are not namespace-qualified. Problem solved. When I discovered this problem, my first idea was to find a fix and propose it for inclusion in Clojure. But I didn’t find any, so I wrote this post as a kind of public warning.

However, Rich Hickey, Clojure’s creator, did find a fix, and applied it immediately. If you work with the master branch of Clojure’s github repository and pull in today’s changes, the code in the example will work just fine. This may be the quickest fix of something never reported as a bug!

So what’s the trick? Clojure now appends # to the function argument symbols in expanded function literals. Syntax-quote treats such symbols specially, replacing them by guaranteed-to-be-unique generated symbols, which moreover are not namespace-qualified. Problem solved.

]]> Comment on Generating deftype forms in macros by John http://onclojure.com/2010/02/23/generating-deftype-forms-in-macros/#comment-76 John Wed, 24 Feb 2010 00:59:42 +0000 http://onclojure.com/?p=86#comment-76 The thing I don't like about syntax-quote (versus quote) is that it makes the expanded code verbose and unreadable. Then it's hard to debug the macro with macroexpand-1. The thing I don’t like about syntax-quote (versus quote) is that it makes the expanded code verbose and unreadable. Then it’s hard to debug the macro with macroexpand-1.

]]> Comment on Managing namespaces by khinsen http://onclojure.com/2010/02/17/managing-namespaces/#comment-75 khinsen Thu, 18 Feb 2010 10:43:05 +0000 http://onclojure.com/?p=80#comment-75 There's already remove-ns. Combine this with in-ns, and you get the equivalent of emptying a namespace, except that the namespace object changes, rendering aliases invalid. But... what would you use this for in practice? The only namespace I ever wanted to reset is "user", from the REPL. But it's just as easy to make a new one instead. There’s already remove-ns. Combine this with in-ns, and you get the equivalent of emptying a namespace, except that the namespace object changes, rendering aliases invalid.

But… what would you use this for in practice? The only namespace I ever wanted to reset is “user”, from the REPL. But it’s just as easy to make a new one instead.

]]> Comment on Managing namespaces by khinsen http://onclojure.com/2010/02/17/managing-namespaces/#comment-74 khinsen Thu, 18 Feb 2010 10:38:51 +0000 http://onclojure.com/?p=80#comment-74 If modifying the behaviour of the compiler is an option, then it would be sufficient to allow redefining a symbol that currently points to a var in another namespace. I am not sure if that's a good idea though. At least at the REPL level, I like the error message that prevents me from overwriting something accidentally. Perhaps the default behaviour should differ between the REPL and loading from a file. If modifying the behaviour of the compiler is an option, then it would be sufficient to allow redefining a symbol that currently points to a var in another namespace.

I am not sure if that’s a good idea though. At least at the REPL level, I like the error message that prevents me from overwriting something accidentally. Perhaps the default behaviour should differ between the REPL and loading from a file.

]]> Comment on Managing namespaces by Stuart Halloway http://onclojure.com/2010/02/17/managing-namespaces/#comment-73 Stuart Halloway Thu, 18 Feb 2010 08:48:07 +0000 http://onclojure.com/?p=80#comment-73 I created a ticket for this: http://www.assembla.com/spaces/clojure/tickets/272-load-ns-require-use-overhaul and will bring it up on the dev list. I created a ticket for this: http://www.assembla.com/spaces/clojure/tickets/272-load-ns-require-use-overhaul and will bring it up on the dev list.

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