70 lines
2.0 KiB
Standard ML
70 lines
2.0 KiB
Standard ML
signature PARSE_FILE =
|
|
sig
|
|
val parseLine: string -> AppType.triangle option
|
|
end
|
|
|
|
structure ParseFile :> PARSE_FILE =
|
|
struct
|
|
datatype triangle_token = X | Y | COORD of Real32.real | UNKNOWN of string
|
|
|
|
fun extractTriangle lst =
|
|
case lst of
|
|
[ X, COORD x1
|
|
, Y, COORD y1
|
|
, X, COORD x2
|
|
|
|
, Y, COORD y2
|
|
, X, COORD x3
|
|
, Y, COORD y3
|
|
] => SOME {x1 = x1, y1 = y1, x2 = x2, y2 = y2, x3 = x3, y3 = y3}
|
|
| _ => NONE
|
|
|
|
fun tokeniseString str =
|
|
if str = "x" then
|
|
X
|
|
else if str = "y" then
|
|
Y
|
|
else
|
|
case Real32.fromString str of
|
|
SOME num => COORD num
|
|
| NONE => UNKNOWN str
|
|
|
|
fun helpParseLine (line, pos, acc, wordStartPos) =
|
|
if pos = String.size line then
|
|
List.rev acc
|
|
else
|
|
let
|
|
val chr = String.sub (line, pos)
|
|
in
|
|
if Char.isSpace chr then
|
|
if pos > 0 andalso Char.isSpace (String.sub (line, pos - 1)) then
|
|
(* if previous character is space, just proceed to next character *)
|
|
helpParseLine (line, pos + 1, acc, wordStartPos)
|
|
else
|
|
let
|
|
(* current character is space, but previous character is not,
|
|
* which means we have some text to substring and tokenise
|
|
* before proceeding to next character *)
|
|
val strToken =
|
|
String.substring (line, wordStartPos, pos - wordStartPos)
|
|
val token = tokeniseString strToken
|
|
in
|
|
helpParseLine (line, pos + 1, token :: acc, pos)
|
|
end
|
|
else if pos > 0 andalso Char.isSpace (String.sub (line, pos - 1)) then
|
|
(* previous character was space but current character is not,
|
|
* meaning that we have hit the start of a new word *)
|
|
helpParseLine (line, pos + 1, acc, pos)
|
|
else
|
|
(* just proceed to next character *)
|
|
helpParseLine (line, pos + 1, acc, wordStartPos)
|
|
end
|
|
|
|
fun parseLine line =
|
|
let
|
|
val lst = helpParseLine (line, 0, [], 0)
|
|
in
|
|
extractTriangle lst
|
|
end
|
|
end
|