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digitalmars.D - friend functions...

reply Peter Tkacz <Peter_member pathlink.com> writes:
I've been doing some reading, and don't recall having seen anything on friend
functions.  I also haven't done any programming in D, but would like to except
avoid it until my other work has been completed, on one may as well label it the
100 year project.

I do notice that there are the usual functions sine(real), cos(real), etc..  I
also assume that the functions are utilized as y = sin(x);.

So my question is then, if I was to create my own type myReal, with it's complex
inner workings, how do I would an external function to the class have access to
it's inner workings?
May 04 2004
parent reply "Matthew" <matthew.hat stlsoft.dot.org> writes:
"Peter Tkacz" <Peter_member pathlink.com> wrote in message
news:c79bpt$1tlh$1 digitaldaemon.com...
 I've been doing some reading, and don't recall having seen anything on friend
 functions.  I also haven't done any programming in D, but would like to except
 avoid it until my other work has been completed, on one may as well label it

 100 year project.

 I do notice that there are the usual functions sine(real), cos(real), etc..  I
 also assume that the functions are utilized as y = sin(x);.

 So my question is then, if I was to create my own type myReal, with it's

 inner workings, how do I would an external function to the class have access to
 it's inner workings?

I think such things can be done by being in the same module, but I'm not sure as I haven't tried. I think the need for friend declarations are almost never borne out. I'm firmly in the Scott Meyers camp (http://www.cuj.com/documents/s=8042/cuj0002meyers/) on this one, and only ever use friend for (C++) class sharing the same header file. Since the only classes that share header files should be those that are logically inextricably linked, such as containers and their iterator/value-type classes (see the WinSTL file / reg enumeration classes for examples; http://stlsoft.org/), this is pretty rare indeed. Anyway, blather, blather. D doesn't have a friend keyword, but you can get it using modules, but you shouldn't want it other than in rare cases. Yours didactically, Matthew
May 04 2004
parent Mike Swieton <mike swieton.net> writes:
On Wed, 05 May 2004 10:42:44 +1000, Matthew wrote:
 I think the need for friend declarations are almost never borne out. I'm
 firmly in the Scott Meyers camp
 (http://www.cuj.com/documents/s=8042/cuj0002meyers/) on this one, and
 only ever use friend for (C++) class sharing the same header file. Since
 the only classes that share header files should be those that are
 logically inextricably linked, such as containers and their
 iterator/value-type classes (see the WinSTL file / reg enumeration
 classes for examples; http://stlsoft.org/), this is pretty rare indeed.
 
 Anyway, blather, blather. D doesn't have a friend keyword, but you can
 get it using modules, but you shouldn't want it other than in rare
 cases.
 
 

tests, since there's no package/module-private level in C++. But in java we just use package private and in D we'd probably do the same. In other words, I agree: D has no need for a friend keyword. I would be extremely interested to see any counterexample. Mike Swieton __ The perversity of the Universe tends towards a maximum. - O'Tool's Corollary of Finagle's Law
May 04 2004