literate: adding some literate programming ideas.

extra/literate/authors.txt

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+John Benediktsson

extra/literate/literate.factor

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+! Copyright (C) 2012 John Benediktsson
+! See http://factorcode.org/license.txt for BSD license
+USING: accessors combinators.short-circuit compiler.units kernel
+lexer math multiline parser sequences splitting ;
+
+IN: literate
+
+TUPLE: literate-lexer < lexer ;
+
+: <literate-lexer> ( text -- lexer ) literate-lexer new-lexer ;
+
+M: literate-lexer skip-blank
+    dup column>> zero? [
+        dup line-text>> [
+            "> " head?
+            [ [ 2 + ] change-column call-next-method ]
+            [ [ nip length ] change-lexer-column ]
+            if
+        ] [ drop ] if*
+    ] [ call-next-method ] if ;
+
+SYNTAX: <LITERATE
+    "LITERATE>" parse-multiline-string string-lines [
+        <literate-lexer> (parse-lines) over push-all
+    ] with-nested-compilation-unit ;

extra/literate/summary.txt

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+Literate programming techniques