🚀 go-pugleaf

matt@godzilla.EECS.Berkeley.EDU (Matt Austern) writes:

>In article <4638jp$ef4@fsgm01.fnal.gov> b91926@fsgm01.fnal.gov (David Sachs) w
rites:

>> X x(a) uses higher priority conversion by overloading rules
>> 
>> X x=a uses X(a.operator X&)

>Sort of.  If a is of class A, if the copy constructor X::X(const X&)
>exists, and if the converting constructor X::X(const A&) exists and
>isn't qualified as explicit, then "X x(a)" simply invokes the
>converting constructor while "X x=a" invokes the converting
>constructor and then the copy constructor.

>Section 12.6 of the working paper explains this in detail.  The rest
>of chapter 12 is somewhat relevant too.

If X had a constructor X(A&), there might be some ambiguity, but
suppose X has a constructor X(B&), where B is a unique base class of
A.

Then X x(a); means X X(B&(a)); as trying X(a.operator X&()) would use
a lower priority user conversion.

X x = a; should use the direct conversion function.
-- 
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