Question

Relizing there’s no such thing as a BOOL datatype, take the following:

std::cout << (1>2); //<<-- prints 0

Assuming this false comparison is a 0, what datatype deos the result of a comparison reduce to? Doing a quick google search doesn’t yield any results. My best guess it that it’s an unsigned char because it’s the smallest most basic datatype where 0 truly represented as 0x00. I don’t want to assume anything because I’m not sure what voodoo std::cout does to the value to make it a printable character.

Answer 1

The type of the result of all relational operators (<, >, <=, >=) is bool:

The operators < (less than), > (greater than), <= (less than or equal to), and >= (greater than or equal to) all yield false or true. The type of the result is bool.

An object of type bool has the values true or false.Under integral promotion, a bool can be converted to an int where false becomes 0 and true becomes 1:

A prvalue of type bool can be converted to a prvalue of type int, with false becoming zero and true becoming one.

bool is an integral type, which the standard says are represented by use of a “pure binary numeration system”. The footnote that describes this representation is fairly unclear as to how it maps to the values true and false, but you could assume that they are implying that the value representation for 0 would be all 0 bits:

A positional representation for integers that uses the binary digits 0 and 1, in which the values represented by successive bits are additive, begin with 1, and are multiplied by successive integral power of 2, except perhaps for the bit with the highest position. (Adapted from the American National Dictionary for Information Processing Systems.)