escape-strings: Add a way to find minmal escapes for a lua/magic

string.

basis/escape-strings/authors.txt

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+John Benediktsson
+Doug Coleman

basis/escape-strings/escape-strings-tests.factor

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+! Copyright (C) 2017 John Benediktsson, Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: tools.test escape-strings ;
+IN: escape-strings.tests
+
+{ "[[asdf]]" } [ "asdf" escape-string ] unit-test
+{ "[[[[]]" } [ "[[" escape-string ] unit-test
+{ "[=[]]]=]" } [ "]]" escape-string ] unit-test
+
+{ "[===[]]]==][=[=]=]]===]" } [ "]]]==][=[=]=]" escape-string ] unit-test
+{ "[[[=[=]=]]]" } [ "[=[=]=]" escape-string ] unit-test
+{ "[[[a[]]" } [ "[a[" escape-string ] unit-test

basis/escape-strings/escape-strings.factor

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+! Copyright (C) 2017 John Benediktsson, Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: combinators kernel math math.order sequences ;
+IN: escape-strings
+
+! TODO: Move the "]]" subseq? check into the each loop logic
+: #escapes ( str -- n/f )
+    [ f f f ] dip [
+        {
+            { char: = [ [ dup [ 1 + ] when ] bi@ ] }
+            { char: ] [ [ [ 0 or ] 2dip [ max ] curry dip ] when* 0 ] }
+            [ 2drop f ]
+        } case
+    ] each 2drop ;
+
+: escape-string ( str -- str' )
+    "]]" over subseq? [
+        dup #escapes ?1+ char: = <repetition>
+        [ "[" dup surround ] [ "]" dup surround ] bi surround
+    ] [
+        "[[" "]]" surround
+    ] if ;