Shriramana Sharma wrote: > operator-notequal.cpp:14: error: no match for ‘operator!=’ in ‘a != b’ > > Now there need conceivably be no definition for operator != other than > the not-ted value of what operator == gives, so why does gcc want me to > define operator != separately? > > Similarly even if I define only operator !=, gcc will tell me to > separately define operator == if I want to use that. > > For the pairs: > > == and != > > and <= > < and >= > > it is mathematically illogical to have any definition for each operator > in the pair which does not output same as the not-ted output of the > other operator in the pair, In terms of mathematics, that's not even remotely true, particularly for the inequalities (totally-ordered vs partially-ordered). In C/C++ terms, it isn't necessarily true for the standard types; e.g. if floating-point values x and y are both NaN, then both x==y and x!=y are false. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
