when parsing NFA, label position of leaves (each leaf is either a CHAR_LITERAL or a WILDCARD)
This commit is contained in:
@@ -1,14 +1,14 @@
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structure Nfa =
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struct
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datatype regex =
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CHAR_LITERAL of char
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CHAR_LITERAL of {char: char, position: int}
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| CONCAT of regex list
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| ALTERNATION of regex list
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| ZERO_OR_ONE of regex
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| ZERO_OR_MORE of regex
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| ONE_OR_MORE of regex
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| GROUP of regex
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| WILDCARD
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| WILDCARD of int
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structure ParseNfa =
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struct
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@@ -37,15 +37,15 @@ struct
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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) : (int * regex) option =
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fun climb (pos, str, lhs, level, stateNum) : (int * regex * int) option =
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if pos = String.size str then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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case String.sub (str, pos) of
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#")" => SOME (pos + 1, lhs)
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#")" => SOME (pos + 1, lhs, stateNum)
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| #"(" =>
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if level < groupLevel then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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(case getRightParenIdx (pos + 1, str) of
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SOME groupEndIdx =>
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@@ -53,34 +53,40 @@ struct
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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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(case parse (substr, stateNum) of
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SOME (rhs, stateNum) =>
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let
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val rhs = GROUP rhs
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val result = CONCAT [lhs, rhs]
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in
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climb (groupEndIdx + 1, str, result, groupLevel)
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climb
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( groupEndIdx + 1
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, str
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, result
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, groupLevel
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, stateNum
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)
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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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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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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
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val chr = CHAR_LITERAL {char = chr, position = stateNum + 1}
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in
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case climb (pos + 2, str, chr, altLevel) of
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SOME (pos, rhs) =>
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case climb (pos + 2, str, chr, altLevel, stateNum + 1) of
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SOME (pos, rhs, stateNum) =>
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let
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val result =
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case rhs of
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ALTERNATION lst => ALTERNATION (lhs :: lst)
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| _ => ALTERNATION [lhs, rhs]
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in
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SOME (pos, result)
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SOME (pos, result, stateNum)
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end
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| NONE => NONE
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end
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@@ -88,68 +94,74 @@ struct
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NONE
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| #"?" =>
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if level < postfixLevel then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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let val lhs = ZERO_OR_ONE lhs
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in climb (pos + 1, str, lhs, postfixLevel)
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in climb (pos + 1, str, lhs, postfixLevel, stateNum)
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end
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| #"*" =>
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if level < postfixLevel then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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let val lhs = ZERO_OR_MORE lhs
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in climb (pos + 1, str, lhs, postfixLevel)
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in climb (pos + 1, str, lhs, postfixLevel, stateNum)
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end
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| #"+" =>
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if level < postfixLevel then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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let val lhs = ONE_OR_MORE lhs
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in climb (pos + 1, str, lhs, postfixLevel)
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in climb (pos + 1, str, lhs, postfixLevel, stateNum)
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end
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| chr =>
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if level < concatLevel then
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SOME (pos, lhs)
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SOME (pos, lhs, stateNum)
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else
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let
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val currentState =
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if chr = #"." then WILDCARD else CHAR_LITERAL chr
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if chr = #"." then WILDCARD (stateNum + 1)
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else CHAR_LITERAL {char = chr, position = stateNum + 1}
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in
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case climb (pos + 1, str, currentState, concatLevel) of
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SOME (pos, rhs) =>
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case
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climb (pos + 1, str, currentState, concatLevel, stateNum + 1)
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of
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SOME (pos, rhs, stateNum) =>
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let
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val result =
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case rhs of
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CONCAT lst => CONCAT (lhs :: lst)
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| _ => CONCAT [lhs, rhs]
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in
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SOME (pos, result)
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SOME (pos, result, stateNum)
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end
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| NONE => NONE
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end
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and loop (pos, str, ast) =
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and loop (pos, str, ast, stateNum) =
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if pos = String.size str then
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SOME ast
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SOME (ast, stateNum)
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else
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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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case climb (pos, str, ast, altLevel, stateNum) of
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SOME (pos, ast, stateNum) => loop (pos, str, ast, stateNum)
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| NONE => NONE
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and parse str =
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and parse (str, stateNum) =
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if String.size str > 0 then
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(* todo: we currently assume that the first char is always a CHAR_LITERAL
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* but we should actually check what character the chr is
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* before deciding it represents one variant or another *)
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let
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val chr = String.sub (str, 0)
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val chr = CHAR_LITERAL chr
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val chr = CHAR_LITERAL {char = chr, position = stateNum + 1}
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in
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loop (1, str, chr)
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loop (1, str, chr, stateNum + 1)
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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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fun parse str =
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case ParseNfa.parse (str, 0) of
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SOME (ast, _) => SOME ast
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| NONE => NONE
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end
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