20 General utilities library [utilities]

20.16 Compile-time rational arithmetic [ratio]

20.16.6 SI types for ratio [ratio.si]

For each of the typedef-names 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.