• d-bugmail puremagic.com Apr 29 2008
• d-bugmail puremagic.com Apr 29 2008
• d-bugmail puremagic.com May 01 2008

http://d.puremagic.com/issues/show_bug.cgi?id=2058

           Summary: Describe hidden value passed to class member functions
           Product: D
           Version: 2.012
          Platform: PC
               URL: http://www.digitalmars.com/d/2.0/class.html
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: www.digitalmars.com
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: jlquinn us.ibm.com


As in C++, D appears to implicitly pass a reference to the class instance into
a call to a member function to support references to class member vars and
"this".

The fact that a hidden var is passed in is documented in reference to nested
classes, but not for basic member functions.

This behavior is likely well known to experienced c++ developers, but needs to
be documented in a language spec.

I ran into this trying to pass a class member function into
std.algorithm.lowerBound, which of course doesn't work because of the hidden
class reference.  (There needs to be a way to pass a member function in easily
- subject for another bug).


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=2058





------- Comment #1 from bugzilla digitalmars.com  2008-04-29 15:00 -------
Passing in a member function is easy - they pass as delegate types, rather than
function pointer types.


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=2058





------- Comment #2 from jlquinn us.ibm.com  2008-05-01 10:42 -------
I eventually figured out how to use a delegate here.  I had been working too
hard at it.

At this point, I'm thinking the issue is that lowerBound is specified with
"alias less", which doesn't really tell a newbie what is really safe to pass
in.  Some more detailed docs with basic examples would help, both using
standalone functions, and delegates.  This is really more a meta issue for
stuff in algorithms and other places that can take function references of
various forms.


--