Define ICSi(F) as follows:
— if F is a static member function, ICS1(F) is defined such that ICS1(F) is neither better nor worse than ICS1(G) for any function G, and, symmetrically, ICS1(G) is neither better nor worse than ICS1(F)122);
otherwise,
— let ICSi(F) denote the implicit conversion sequence that converts the ith argument in the list to the type of the ith parameter of viable function F. 13.3.3.1 defines the implicit conversion sequences and 13.3.3.2 defines what it means for one implicit conversion sequence to be a better conversion sequence or worse conversion sequence than another.
Given these definitions, a viable function F1 is defined to be a better function than another viable function F2 if for all arguments i, ICSi(F1) is not a worse conversion sequence than ICSi(F2), and then
— for some argument j, ICSj(F1) is a better conversion sequence than ICSj(F2), or, if not that,
— F1 is a nontemplate function and F2 is a template function specialization, or, if not that,
— F1 and F2 are template functions, and the function template for F1 is more specialized than the template for F2 according to the partial ordering rules described in 14.5.5.2, or, if not that,
— the context is an initialization by userdefined conversion (see 8.5, 13.3.1.5) and the standard conversion sequence from the return type of F1 to the destination type (i.e., the type of the entity being initialized)
is a better conversion sequence than the standard conversion sequence from the return type of F2 to the destination type. [Example:
Code:
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| struct A {
A();
operator int();
operator double();
} a;
int i = a; // a.operator int() followed by no conversion
// is better than a.operator double() followed by
// a conversion to int
float x = a; // ambiguous: both possibilities require conversions,
// and neither is better than the other |
—end example]
2 If there is exactly one viable function that is a better function than all other viable functions, then it is the one selected by overload resolution; otherwise the call is illformed123).
