----- 
permalink: concatenative-020
filters_pre: 
- erb
- redcloth
title: Concatenative 0.2.0 released
date: 2009-04-19 09:42:00 +02:00
tags: 
- ruby concatenative
type: article
-----
Version 0.2.0. of the "Concatenative":/concatenative DSL has been "released":http://rubyforge.org/frs/?group_id=8068&release_id=33575. 

Here are some highlights from the changelog:

* Implemented new combinators:
** binrec
** split
** twodip
** threedip
* Performance improvements:
** Stack is never copied.
** No symbol/string conversion when processing words.
* Pseudo-namespace support (e.g. :kernel/:while and :math/:factorial)
* ~ and <= operators to unquote and define words, respectively.
* No more uppercase words!

Oddly enough, I realized that it is possible to defined methods named after reserved words like "while" or "if", so now all the concatenative words (combinators) in @kernel.rb@ are now defined _without_ a leading undersore. Similarly, there's no real need to use UPPERCASE symbols, so as a result, method lookup is significantly faster and will use less resources.

Here's how the lookup works. Say you have the following program: 

<% highlight :ruby do %>
[[1,2,3], [4.5.6], :concat]
<% end %>

If @:concat@ has been defined by the user (@:concat <= [...]@), that definition will be used, otherwise the @Concatenative::Kernel@ combinator @concat@ will be called. If you want to use the corresponding Ruby method, all you have to do is specifying the arity explicitly using the @|@ operator.

To remove any ambiguity, it is now possible to specify the _namespace_ of a word explicitly, e.g. :kernel/:concat or :ruby/concat. The @/@ operator simply concatenates the two symbols together (@:"kernel/concat"@) and sets the namespace (@:kernel@) and name (@:concat@) of the new symbol. @:kernel@ and @:ruby@ are not meant to be used when defining new words, but you can use anything else you like, for example :math/:factorial or :local/:a, etc.

As I pointed out in the "first article":/articles/concatenative-programming-in-ruby about concatenative, even with the new performance improvement a concatenative program still runs slower than a standard Ruby program, but at least now you won't run out of stack space (the _Ruby_ stack, in this case) too soon.

If you have any issues to report, feature requests, etc., feel free to use "GitHub":http://github.com/h3rald/concatenative/issues to do so.