parser: allow semicolons to finish arguments early

Similarly to how parentheses are omitted at the end of commands, this
change allows them to be omitted at the end of function arguments.
Notice however than this omission is *ambiguous* when the parser does
not know in advance the number of arguments.

  GCD(Ent(x;y -> GCD(Ent(x;y))
              -> GCD(Ent(x);y)

The fx-92 SC+ parser knows the number of arguments for each function,
and will use the second interpretation, because Ent() has one argument
and GCD() has two. This interpreter, however, uses a generic extensible
construction for function calls and cannot decide on this ground. The
current interpretation is the first.

fx92/drawing.py

@@ -199,7 +199,7 @@ class Window:
         """Push window contents on-screen."""
 
         if self.stream:
-            name = "{:04d}.png".format(self.streamid)
+            name = "{:04d}.bmp".format(self.streamid)
             self.save(os.path.join(self.stream, name))
             self.streamid += 1
 

fx92/parser.py

@@ -249,7 +249,7 @@ class Parser:
             e = self.expr()
 
             # Allow a parenthesis to be removed at the end of a parameter
-            optional = (self.la.type == T.PARAM)
+            optional = (self.la.type in [T.PARAM, T.SEMI])
             self.expect(T.RPAR, optional=optional)
             return Node(N.EXP, a, e)
 
@@ -270,7 +270,7 @@ class Parser:
             e = self.expr()
 
             # Allow a parenthesis to be removed at the end of a parameter
-            optional = (self.la.type == T.PARAM)
+            optional = (self.la.type in [T.PARAM, T.SEMI])
             self.expect(T.RPAR, optional=optional)
             return e
 
@@ -279,7 +279,7 @@ class Parser:
             a = self.funargs()
 
             # Allow a parenthesis to be removed at the end of a parameter
-            optional = (self.la.type == T.PARAM)
+            optional = (self.la.type in [T.PARAM, T.SEMI])
             self.expect(T.RPAR, optional=optional)
 
             return Node(N.FUN, name, a)