But... I don't want my delegates to be lazy - breeding advice

[Derek Parnell]

On Tue, 22 Aug 2006 18:39:57 +0100, Tom S wrote:

> Walter, if you *really* want to keep lazy expression evaluation in its 
> current form, then please *at least* don't force everyone to use it.

Amen to that! 

> Adopting delegate function parameters for lazy expressions is a mistake. 

Well ... its the implicit conversion of expressions to delegates that
concerns me. I can see that most of the time it should be harmless, but it
still opens the window of opportunity for seriously long debugging
sessions.

> At least consider adding a new keyword, e.g. 'lazy' or 'expression', 
> please. The syntax could look like:
> 
> void foo(int expression() foo) {
> }
> 
> or
> 
> void foo(lazy int foo) {
> }

or ...

  void foo( delegate int () foo) {}
  void foo( expression int () foo) {}


> or just some other variant. Delegates would then be delegates and 
> wouldn't accept lazy expressions. But lazy expressions could accept 
> delegates.
> 
> The above approach has three significant advantages over the current 
> state of things:
> 
> 1. When the coder doesn't intend to use lazy expression evaluation, 
> his/her functions that take delegates as params won't silently accept 
> lazily evaluated expressions

A big plus, in the manner of "least surprise".

> 2. Less existing code will be broken or the changes will be easier to 
> fix - renaming the keyword to some other variable name compared to the 
> nontrivial fixes that have to be done now.

This also enhances understanding when reading someone else's code. It
allows better understanding of the coder's intentions.

> 3. In future, the 'expression' or 'lazy' types might provide meta-data 
> allowing advanced metaprogramming techniques

Hmmm ... interesting.
 

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
23/08/2006 2:30:50 PM