60 lines
1.8 KiB
Standard ML
60 lines
1.8 KiB
Standard ML
structure ViLDfa =
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struct
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val startState: Word8.word = 0w0
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val notNewlineState: Word8.word = 0w1
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val oneNewlineState: Word8.word = 0w2
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val twoNewlineState: Word8.word = 0w3
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fun makeStart i =
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if Char.chr i = #"\n" then oneNewlineState else notNewlineState
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fun makeOneNewline i =
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if Char.chr i = #"\n" then twoNewlineState else notNewlineState
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val startTable = Vector.tabulate (255, makeStart)
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val notNewlineTable = startTable
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val oneNewlineTable = Vector.tabulate (255, makeOneNewline)
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val twoNewLineTable = startTable
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val tables = #[startTable, notNewlineTable, oneNewlineTable, twoNewLineTable]
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fun next (currentState, chr) =
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let val table = Vector.sub (tables, Word8.toInt currentState)
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in Vector.sub (table, Char.ord chr)
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end
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structure ViL =
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MakeNextDfaLoop
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(struct
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val startState = startState
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fun loop (idx, absIdx, str, tl, currentState, counter) =
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if idx = String.size str then
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case tl of
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str :: tl => loop (0, absIdx, str, tl, currentState, counter)
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| [] => absIdx
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else
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let
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val chr = String.sub (str, idx)
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val newState = next (currentState, chr)
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in
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if newState = twoNewlineState then
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if counter - 1 = ~1 then
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absIdx - 1
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else
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loop (idx + 1, absIdx + 1, str, tl, startState, counter - 1)
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else if newState = notNewlineState then
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if counter - 1 = ~1 then
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absIdx
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else
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loop (idx + 1, absIdx + 1, str, tl, startState, counter - 1)
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else
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loop (idx + 1, absIdx + 1, str, tl, newState, counter)
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end
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val fStart = loop
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end)
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val next = ViL.next
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end
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