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RE: CamlTk and LablTk
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Date: 2000-06-03 (07:33)
From: Dave Berry <dave@k...>
Subject: RE: CamlTk and LablTk
(I hope you don't mind me replying to a fairly old message).

This was a very interesting question, and the examples that Pierre included
were illuminating.  Would it be possible to elucidate a little further?  In
particular, I'd appreciate it if someone could give the types of the
relevant functions in each library.  (At some point one has to look at the
documentation for all the details, but this seems like a reasonably
educational example to take a little further).

Let's compare the two calls to create_oval.  First the Caml/TK:
      Canvas.create_oval c
        (Pixels (cx - wx)) (Pixels (cy - wy))
        (Pixels (cx + wx)) (Pixels (cy + wy))
        [Outline (NamedColor "black"); Width (Pixels 7);
         FillColor (NamedColor "white")]
Second the Labl/TK:
        ~x1:(cx - wx) ~y1:(cy - wy)
        ~x2:(cx + wx) ~y2:(cy + wy) 
        ~outline: `Black ~width: 7
        ~fill: `White

It seems that Labl/TK is using labels in two ways.  First, to have named
arguments, so that you can see which position is x1, which is y1, etc.
Second, to handle optional arguments.  Where Caml/TK takes a list of
attributes, Labl/TK takes extra parameters.  I assume that this is where
Labl/TK has better type checking.  Does the type of each function list the
optional parameters that it may take?  : Doesn't this lead to large types
for each function? (I don't know O'Labl at all well).