Path: utzoo!attcan!uunet!mcsun!ub4b!kulcs!herman
From: herman@kulcs.uucp (Herman Moons)
Newsgroups: comp.lang.c++
Subject: const member functions: why bother the programmer?
Message-ID: <2026@kulcs.kulcs.uucp>
Date: 23 Jul 90 15:45:24 GMT
Organization: Kath.Univ.Leuven, Comp. Sc., Belgium
Lines: 43


Why does the C++ language demand that the programmer states which 
member functions are const ??  This seems a job for the compiler, not
for the programmer (after all, the compiler checks whether a function is
really const if we specify it that way).

I guess the const keyword is needed to tell the compiler about the const'ness
of a member function when it is invoked for a const class object (the member
function is perhaps implemented in another file, where the compiler cannot
see it).

But why not encode the const-info into the function name, just like the
parameter type info ??  A member function f that is const (which can be
determined by the compiler) could than be given two entries in the symbol
table, one with and one without the const-info.

    e.g.  f   T    0xaaaaa     --- entry 1
          C_f T    0xaaaaa     --- entry 2

When a non-const object calls f(), entry 1 is looked up.  When a const object
calls f(), a call for C_f is made.  When the member function was not const,
the C_f info would not have been generated, and a link error would occur.

Without the const keyword, errors would also be catched (at link time, and
not at compile time).  So why bother the programmer with these technicalities.

What really bothers me about const member functions is that one must provide
the compiler with information that he already knows.  
Any opinions on this topic ??

herman

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Herman Moons                                   Katholieke Universiteit Leuven
                                               Dept. of Computer Science
Tf : +32 (16) 20.06.56                         Celestijnenlaan 200A
Fax: +32 (16) 20.53.08                         B-3030 Heverlee-Leuven
                                               Belgium
e-mail: herman@kulcs.uucp
	herman@blekul60.bitnet
	herman@cs.kuleuven.ac.be

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