Expressing Abstraction - Abstracting Expression
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Ola Bini works as a language geek for ThoughtWorks in Chicago. He is one of the JRuby core developers and has been involved in JRuby development since 2006. Ola has created two languages: Ioke and Seph. He’s author of Practical JRuby on Rails Projects and co-author of Using JRuby for the Pragmatic Programmers, a contributor to many open source projects, and a member of the JSR292 Expert Group.
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Very interesting talk
by
Faisal Waris
To provide a flavor, below is the main recursive loop of an experimental HTML parser written with F# 'Active Patterns' (note WS=whitespace; GT = '>'; LT = '<'; Slash = '/', etc.)
let rec (|Html|) inp acc =
match inp with
| WS (ws, rest) -> (|Html|) rest (WS(ws)::acc)
| LT (Exclaim (PI (p, (GT rest)))) -> (|Html|) rest (PI(p)::acc)
| Script (attrs,body,rest) -> (|Html|) rest (Script(attrs,body)::acc)
| LT (Name (n, Attributes (attrs, IgnoreWS restof))) ->
match restof with
| Slash (GT rest) -> (|Html|) rest (Tag(n,attrs)::acc)
| GT rest -> (|Html|) rest (StartTag(n,attrs)::acc)
| _ -> errorOut restof acc
| LT (Slash (Name (n, (IgnoreWS (GT rest))))) -> (|Html|) rest (EndTag(n)::acc)
| Content (cntnt,rest) -> (|Html|) rest (Content(cntnt)::acc)
| Eof _ -> acc|>List.rev
| _ -> errorOut inp acc
When a pattern is matched, the right side of the "->" is executed. In this case the loop is just collecting html tags in a structured way.
More here fshtml.codeplex.com
Re: Very interesting talk
by
Faisal Waris
I started with the algorithm paper by Michael Porter and just transcribed that to code, section by section. This is good example of expressability in my opinon.
Details here: fwaris.wordpress.com/2012/10/30/porter-stemmer-...
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