An implicit conversion sequence is the sequence of conversions required to convert an argument in a function call to the type of the corresponding parameter in a function declaration.
The compiler will try to determine an implicit conversion sequence for each argument. It will then categorize each implicit conversion sequence in one of three categories and rank them depending on the category. The compiler will not allow any program in which it cannot find an implicit conversion sequence for an argument.
The following are the three categories of conversion sequences in order from best to worst:
Note:Two standard conversion sequences or two user-defined conversion sequences may have different ranks.