slight refactoring (move pure parsing functions to functional core in a separate file)

functional-core/file/parse-file.sml

@@ -0,0 +1,55 @@
+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, lastSpacePos) =
+    if pos = String.size line then
+      List.rev acc
+    else
+      let
+        val chr = String.sub (line, pos)
+      in
+        if chr = #" " orelse chr = #"\n" then
+          let
+            val strToken = String.substring
+              (line, lastSpacePos + 1, pos - (lastSpacePos + 1))
+            val token = tokeniseString strToken
+          in
+            helpParseLine (line, pos + 1, token :: acc, pos)
+          end
+        else
+          helpParseLine (line, pos + 1, acc, lastSpacePos)
+      end
+
+  fun parseLine line =
+    let val lst = helpParseLine (line, 0, [], ~1)
+    in extractTriangle lst
+    end
+end