allow loading of files with or without rgb colour data

functional-core/file/parse-file.sml

@@ -5,7 +5,7 @@ end
 
 structure ParseFile :> PARSE_FILE =
 struct
-  datatype triangle_token = X | Y | COORD of Real32.real | UNKNOWN of string
+  datatype triangle_token = X | Y | R | G | B | COORD of Real32.real | UNKNOWN of string
 
   val zero: Real32.real = 0.0
 
@@ -26,6 +26,7 @@ struct
       , Y
       , COORD y3
       ] =>
+        (* file format not specifying any colours *)
         SOME
           { x1 = x1
           , y1 = y1
@@ -37,6 +38,40 @@ struct
           , g = zero
           , b = zero
           }
+    | [ X
+      , COORD x1
+      , Y
+      , COORD y1
+
+      , X
+      , COORD x2
+      , Y
+      , COORD y2
+
+      , X
+      , COORD x3
+      , Y
+      , COORD y3
+
+      , R
+      , COORD r
+      , G
+      , COORD g
+      , B
+      , COORD b
+      ] =>
+        (* file format specifying rgb *)
+        SOME
+          { x1 = x1
+          , y1 = y1
+          , x2 = x2
+          , y2 = y2
+          , x3 = x3
+          , y3 = y3
+          , r = r
+          , g = g
+          , b = b
+          }
     | _ => NONE
 
   fun tokeniseString str =
@@ -44,6 +79,12 @@ struct
       X
     else if str = "y" then
       Y
+    else if str = "r" then
+      R
+    else if str = "g" then
+      G
+    else if str = "B" then
+      B
     else
       case Real32.fromString str of
         SOME num => COORD num