20 General utilities library [utilities]

20.11 Compile-time rational arithmetic [ratio]

20.11.6 SI types for ratio [ratio.si]

For each of the typedefs yocto, zepto, zetta, and yotta, if both of the constants used in its specification are representable by intmax_t, the typedef shall be defined; if either of the constants is not representable by intmax_t, the typedef shall not be defined.