Lazy eval

[Derek Parnell]

On Mon, 21 Aug 2006 16:33:00 -0700, Walter Bright wrote:

> Frank Benoit wrote:
>> For example i have a container with a add( element ) method. Now this
>> method is implemented with lazy-eval, if the container is already full,
>> the argument is not evaluated.
>> Or the get( index ) method does not eval the arg if the container is
>> empty. And every time I have not only to remember the method name and
>> arguments, now I have to know details of the implementation.
>> Great, that was the silly thing they wanted to take away from me with
>> this OOP ;)
>> 
>> Solution: Force the user the make {} around a delegate argument.
>> 
>> Now I get a compiler error when writing container.get(i++); Then I know,
>> this is a delegate, take care with the increment, writing
>> container.get({i}); i++;
> 
> While I understand your concern, I don't think the examples illustrate 
> it. If a get() is done for an element that doesn't exist, the usual way 
> to deal with it is throw an exception, and have some complex scheme to 
> try and undo the side effects from evaluating the argument. With lazy 
> evaluation, no need to undo the side effects, as only if the get() is 
> guaranteed to succeed will the argument be evaluated.
> 
> The problem with requiring the { } around the argument is that 
> programmers just don't like it. I don't think I can make them like it.

Huh? You asked them all? You didn't ask me and I like it. 
-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
22/08/2006 10:50:15 AM