when parsing a string into an NFA, return an option type if the syntax is invalid
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@@ -240,12 +240,10 @@ struct
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fun buildRange (buffer, searchString, finishIdx) =
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if String.size searchString > 0 then
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let
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val nfa = Nfa.parse searchString
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val startIdx = #idx buffer
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in
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Nfa.getMatchesInRange (startIdx, finishIdx, buffer : LineGap.t, nfa)
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end
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case Nfa.parse searchString of
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SOME nfa =>
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Nfa.getMatchesInRange (#idx buffer, finishIdx, buffer : LineGap.t, nfa)
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| NONE => empty
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else
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empty
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@@ -357,9 +357,7 @@ struct
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structure ParseNfa =
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struct
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(* parsing through precedence climbing algorithm.
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* Todo: return a a `regex option`, and use bounds-checking
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* to ensure we don't raise an exception. *)
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(* parsing through precedence climbing algorithm. *)
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val groupLevel = 1
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val postfixLevel = 2
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@@ -369,107 +367,130 @@ struct
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local
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fun loop (pos, str, openParens, closeParens) =
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if pos = String.size str then
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pos
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NONE
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else
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case String.sub (str, pos) of
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#"(" => loop (pos + 1, str, openParens + 1, closeParens)
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| #")" =>
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if closeParens + 1 = openParens then pos
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if closeParens + 1 = openParens then SOME pos
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else loop (pos + 1, str, openParens, closeParens + 1)
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| _ => loop (pos + 1, str, openParens, closeParens)
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in
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fun getRightParenIdx (pos, str) = loop (pos, str, 1, 0)
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end
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fun climb (pos, str, lhs, level) =
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fun climb (pos, str, lhs, level) : (int * regex) option =
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if pos = String.size str then
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(pos, lhs)
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SOME (pos, lhs)
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else
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case String.sub (str, pos) of
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#")" => (pos + 1, lhs)
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#")" => SOME (pos + 1, lhs)
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| #"(" =>
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if level < groupLevel then
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(pos, lhs)
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SOME (pos, lhs)
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else
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let
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val groupEndIdx = getRightParenIdx (pos + 1, str)
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val substr = String.substring
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(str, pos + 1, groupEndIdx - pos - 1)
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val rhs = parse substr
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val rhs = GROUP (rhs, UNTESTED)
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val result = CONCAT
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([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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climb (groupEndIdx + 1, str, result, groupLevel)
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end
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(case getRightParenIdx (pos + 1, str) of
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SOME groupEndIdx =>
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let
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val substr = String.substring
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(str, pos + 1, groupEndIdx - pos - 1)
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in
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(case parse substr of
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SOME rhs =>
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let
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val rhs = GROUP (rhs, UNTESTED)
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val result = CONCAT
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([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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climb (groupEndIdx + 1, str, result, groupLevel)
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end
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| NONE => NONE)
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end
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| NONE => NONE)
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| #"|" =>
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if level < altLevel then
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(pos, lhs)
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else
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SOME (pos, lhs)
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else if pos + 1 < String.size str then
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let
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val chr = String.sub (str, pos + 1)
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val chr = CHAR_LITERAL (chr, UNTESTED)
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val (pos, rhs) = climb (pos + 2, str, chr, altLevel)
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val result =
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case rhs of
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ALTERNATION (lst, state) =>
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ALTERNATION ((lhs, UNTESTED) :: lst, UNTESTED)
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| _ =>
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ALTERNATION ([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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(pos, result)
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case climb (pos + 2, str, chr, altLevel) of
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SOME (pos, rhs) =>
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let
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val result =
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case rhs of
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ALTERNATION (lst, state) =>
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ALTERNATION ((lhs, UNTESTED) :: lst, UNTESTED)
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| _ =>
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ALTERNATION
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([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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SOME (pos, result)
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end
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| NONE => NONE
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end
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else
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NONE
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| #"?" =>
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if level < postfixLevel then
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(pos, lhs)
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SOME (pos, lhs)
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else
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let val lhs = ZERO_OR_ONE (lhs, UNTESTED)
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in climb (pos + 1, str, lhs, postfixLevel)
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end
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| #"*" =>
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if level < postfixLevel then
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(pos, lhs)
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SOME (pos, lhs)
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else
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let val lhs = ZERO_OR_MORE (lhs, UNTESTED)
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in climb (pos + 1, str, lhs, postfixLevel)
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end
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| #"+" =>
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if level < postfixLevel then
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(pos, lhs)
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SOME (pos, lhs)
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else
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let val lhs = ONE_OR_MORE (lhs, UNTESTED)
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in climb (pos + 1, str, lhs, postfixLevel)
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end
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| chr =>
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if level < concatLevel then
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(pos, lhs)
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SOME (pos, lhs)
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else
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let
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val chr = CHAR_LITERAL (chr, UNTESTED)
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val (pos, rhs) = climb (pos + 1, str, chr, concatLevel)
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val result =
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case rhs of
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CONCAT (lst, _) => CONCAT ((lhs, UNTESTED) :: lst, UNTESTED)
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| _ => CONCAT ([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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(pos, result)
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end
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case
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climb (pos + 1, str, CHAR_LITERAL (chr, UNTESTED), concatLevel)
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of
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SOME (pos, rhs) =>
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let
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val result =
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case rhs of
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CONCAT (lst, _) =>
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CONCAT ((lhs, UNTESTED) :: lst, UNTESTED)
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| _ =>
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CONCAT ([(lhs, UNTESTED), (rhs, UNTESTED)], UNTESTED)
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in
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SOME (pos, result)
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end
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| NONE => NONE
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and loop (pos, str, ast) =
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if pos = String.size str then
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ast
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SOME ast
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else
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let val (pos, ast) = climb (pos, str, ast, altLevel)
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in loop (pos, str, ast)
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end
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case climb (pos, str, ast, altLevel) of
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SOME (pos, ast) => loop (pos, str, ast)
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| NONE => NONE
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and parse str =
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let
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val chr = String.sub (str, 0)
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val chr = CHAR_LITERAL (chr, UNTESTED)
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in
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loop (1, str, chr)
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end
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if String.size str > 0 then
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let
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val chr = String.sub (str, 0)
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val chr = CHAR_LITERAL (chr, UNTESTED)
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in
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loop (1, str, chr)
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end
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else
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NONE
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end
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val parse = ParseNfa.parse
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