On 14 mrt 2005, at 10:48, Michael Van Canneyt wrote:
Procedure iso_fun( function f( x: real): real); begin StoredF:=F; end;
This assignment is invalid, it's the same as trying to assign a method to a regular procedural variable.
This is exactly my point: how does the compiler distinguish the two in this case ?
The same way it distinguishes between a "procedure x(...) of object" and a "procedure x(...)". When parsing the function header and encountering such a declaration, it sets some sort of flag inside the procdef that this is an ISO-style procvar. Later, when trying to assign this to a regular procvar, you'll get a type clash.
I don't see how, unless you add an extra parameter for the 'iso' way of doing things.
So, basically, to be able to use a local procedure as a callback,
- You must declare a function with the ISO way to specify a callback.
- This function is not usable with a global callback function.
-> So if you would want to use such a function for both normal and local
procedures, you would have to implement it twice !
Just like you have to implement functions which you want to be able to use as both "procedure of object" and regular procedural variables twice. We have similar problems in the compiler, with e.g. foreach and foreach_static (and foreachnodestatic).
If this is indeed the case, then it is totally ridiculous in my opinion
to implement such a "feature", because if you must make special amends
_anyway_, then you can just as well do it with global functions, without
the local variants.
So we do away with procedure of object also? :)
I question the usefullness of this whole "feature".
The usefulness is mainly existing code which depends on it. There was no procedure of object in those days. This is like saying that nested procedures are useless because you can make a class with methods to achieve the same result (having multiple functions access the same state, while protecting it from outside prying eyes).
Jonas
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