Re: Modular types inside records

[Robert A Duff <bobduff@world.std.com>]

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niewiap@widzew.net (Pawe� Niewiadomski) writes:

> I don't think that adding a couple of if statements makes the code more 
> readable.

Or a couple of "mod" operators.

>...  On the contrary:  if someone looks at the record and sees a 
> modular type, he says: OK, so I don't have to worry about constraint 
> errors; I can get down to the important stuff.

When I see a modular type, I say: OK, so I don't have to worry about
constraint errors; I have to worry about wrong answers.  Half :-).

>...  My implementations of the 
> empty and full functions are just one-line-long and add and remove 
> procedures each take up as much as five lines of code.  Imagine what they 
> would look like if you had to check for constraint errors every time.

I don't understand that -- you don't *check* for C_E, you write the code
so it doesn't cause C_E.

- Bob