Re: Enumerated data types

> car_colours = (red, blue, brown, black);
> bike_colours = (orange, red, green, white);
> suc (car_colour, red) = blue
> suc (bike_colour, red) = green


> Are there problems with this definition of enumerated data types?
> Could be there difficulties trying to specify the semantics of suc,
> pred and ord?, Any suggestion?


The problems aren't with suc() and pred(), but rather with determining
the type of "red" when the parser sees it in the source. Consider:


procedure foo (b: bike_colour)


foo(red);


In order to determine which type "red" is, we need to consult the definition
of "foo". Does Pascal do this for integer/real constants anyway?


procedure bar (r: real)


bar (12); /* sent in an integer */


Would the 12 be coerced to type real, or will a Pascal compiler flag this
as an error? If it does the coercion, I don't see a problem with overloading
enumerated type names.


If there was a problem, you could always lexically distinguish enumerated
type names. Although it takes some getting used to, you could write


bike_color(blue)


instead of just "blue".


Rich
--
skrenta@blekko.commodore.com
--

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