Differences between std::is_integer and std::is_integral?

Question

C++11 provides two type trait template classes: std::is_integer and std::is_integral. However, I cannot tell the differences between them.

Answer 1

std::is_integral and std::numeric_limits::is_integer are NOT the same. E.g. boost::multiprecision big ints are treated differently.

This is from a corresponding issue:

is_integral returns information about the nature of the type and is true only for "native" integer types, it should never be true for class types. Which is to say is_integer and is_class are mutually exclusive.

numeric_limits on the other hand returns information on the behaviour of a type - whether it models a particular concept if you will - and so should be specialized for UDT's. Note that specializing is_integer for UDTs would break code, since is_integer implies that a lot of other things are also true like trivial move/copy/init etc.