Re: How to overcome overloading ambiguity
"Pascal J. Bourguignon" <pjb@informatimago.com> wrote in message =
news:7cy6rswkgv.fsf@pbourguignon.anevia.com...
"Fred Zwarts" <F.Zwarts@KVI.nl> writes:
In my software I need a vector of boolean values.
My first attempt was to use vector<bool>, but vector has a =
specialization for the bool type
with unwanted implications. For example, I need to pass elements of =
the vector as
reference to bool (bool&) to certain functions which may modify the =
value of such elements.
This is not possible with vector<bool>.
My next idea was to create a class Boolean_t which can be used =
instead of the bool type,
with transparent functionality. So I attempted the following:
class Boolean_t {
Just do:
#include <iostream>
#include <vector>
namespace My { typedef unsigned char Bool; enum { no=0,yes=1 }; }
int main(){
std::vector<My::Bool> v;
v.push_back(My::no);
v.push_back(My::yes);
My::Bool& b=(*(v.begin()));
b=My::yes;
std::cout<<int(v.front())<<" "<<int(v.back())<<std::endl;
return(0);
}
/*
-*- mode: compilation; default-directory: "/tmp/" -*-
Compilation started at Tue Jun 16 12:16:38
SRC="/tmp/b.c++" ; EXE="b" ; g++ -g3 -ggdb3 -o ${EXE} ${SRC} && =
../${EXE} && echo status = $?
1 1
status = 0
Compilation finished at Tue Jun 16 12:16:39
*/
--
__Pascal Bourguignon__
I don't think My::Bool is the transparent replacement for bool that I =
meant.
I can't assign true or false. The sizeof My::Bool may be different from =
the sizeof bool.
I can't use My::Bool in functions that need a reference to bool (bool&) =
parameter.
The Boolean_t class is much more transparent. The only remaining =
problem is the ambiguity
between two functionally equivalent operators. If I remove operator =
bool, everything works
transparently. The bool and Boolean_t types can be interchanged and =
mixed in expressions.
Only it does not work for const objects.
For const objects another (const) conversion function is needed, but I =
don't see
how that can be done without creating a ambiguity.
It would be sufficient to change somehow the precedence arbitrarily so =
that the compiler takes
one of the two.