Explanation of macros; Haskell macros

[Joachim Durchholz]

Alain Picard wrote:

> "Robert Klemme" <bob.news at gmx.net> writes:
> 
>>Just for the sake of my understanding: could one summarize this as "macros
>>make control of *when* something is evaluated easier"?  
> 
> More precisely: "macros make control of when, if, and how often,
>                  something is evaluated _possible_."  
> 
> Functions (your only other option) give you no choice.

This statement is wrong if left in full generality: higher-order 
functions can control quite precisely what gets evaluated when. If the 
language offers both lazy and strict parameters, evaluation time control 
extends to the parameter expressions as well.
It's a different kind of control than macros, of course. (It would be 
interesting to see how things would map from macros to functions and 
vice versa.)

Regards,
Jo