advent-of-code-2021/day-05/01.sml

(* open IntInf; *)


val newline_tokenizer = String.tokens (fn c => c = #"\n");
val points_tokenizer = StringExtra.split " -> ";
val comma_tokenizer = String.tokens (fn c => c = #",");

val str = FileExtra.read "input";
val lines = newline_tokenizer str;
val points_as_str = map points_tokenizer lines;


fun string_to_point str =
    let
        val parts = comma_tokenizer str;
    in
        if (length parts) = 2
        then
            let
                val a = hd parts;
                val b = hd (tl parts);
                val x = case Int.fromString a of
                            SOME num => num
                          | NONE => raise Fail "should not happen";
                val y = case Int.fromString b of
                            SOME num => num
                          | NONE => raise Fail "should not happen";
            in
                (x,y) : LineSegment.point
            end
        else
            raise Fail "not a point"
    end;


fun make_segments nil = []
  | make_segments (points_as_str as (ps_as_strs::rest)) =
    let
        val (p1_str :: p2_str :: nil) = ps_as_strs;
        val p1 = string_to_point p1_str;
        val p2 = string_to_point p2_str;
    in
        LineSegment (p1, p2) :: (make_segments rest)
    end;


val line_segments = make_segments points_as_str;