56 lines
1.3 KiB
Standard ML
56 lines
1.3 KiB
Standard ML
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signature PARSE_FILE =
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sig
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val parseLine: string -> AppType.triangle option
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end
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structure ParseFile :> PARSE_FILE =
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struct
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datatype triangle_token = X | Y | COORD of Real32.real | UNKNOWN of string
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fun extractTriangle lst =
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case lst of
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[ X, COORD x1
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, Y, COORD y1
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, X, COORD x2
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, Y, COORD y2
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, X, COORD x3
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, Y, COORD y3
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] => SOME {x1 = x1, y1 = y1, x2 = x2, y2 = y2, x3 = x3, y3 = y3}
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| _ => NONE
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fun tokeniseString str =
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if str = "x" then
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X
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else if str = "y" then
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Y
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else
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case Real32.fromString str of
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SOME num => COORD num
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| NONE => UNKNOWN str
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fun helpParseLine (line, pos, acc, lastSpacePos) =
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if pos = String.size line then
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List.rev acc
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else
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let
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val chr = String.sub (line, pos)
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in
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if chr = #" " orelse chr = #"\n" then
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let
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val strToken = String.substring
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(line, lastSpacePos + 1, pos - (lastSpacePos + 1))
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val token = tokeniseString strToken
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in
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helpParseLine (line, pos + 1, token :: acc, pos)
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end
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else
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helpParseLine (line, pos + 1, acc, lastSpacePos)
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end
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fun parseLine line =
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let val lst = helpParseLine (line, 0, [], ~1)
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in extractTriangle lst
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end
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end
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