add interpolate

basis/interpolate/authors.txt

@@ -0,0 +1 @@
+Doug Coleman

basis/interpolate/interpolate-tests.factor

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+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: tools.test interpolate ;
+IN: interpolate.tests

basis/interpolate/interpolate.factor

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+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: io kernel macros make multiline namespaces parser
+peg.ebnf present sequences strings ;
+IN: interpolate
+
+MACRO: interpolate ( string -- )
+[EBNF
+var = "${" [^}]+ "}" => [[ second >string [ get present write ] curry ]]
+text = [^$]+ => [[ >string [ write ] curry ]]
+interpolate = (var|text)* => [[ [ ] join ]]
+EBNF] ;
+
+EBNF: interpolate-locals
+var = "${" [^}]+ "}" => [[ [ second >string search , [ present write ] % ] [ ] make ]]
+text = [^$]+ => [[ [ >string , [ write ] % ] [ ] make ]]
+interpolate = (var|text)* => [[ [ ] join ]]
+;EBNF
+
+: I[ "]I" parse-multiline-string
+    interpolate-locals parsed \ call parsed ; parsing