[Cfp-interest] quantexp (or …) for Part 3

[James W Thomas]

At the May CFP teleconference we decided for Part 3 to add quantum-exponent functions that return in a decimal type and for Part 2 to retain its current quantexpd[32|64|128] functions that return int. What to name the new functions?

Following the naming pattern of using a prefix to reflect the return type, we might have dquantexp or decquantexp. In other <math.h> cases, this prefix convention is used to indicate integer type returns (ilogb, lrint, etc.), instead of the presumed floating type returns (logb, rint, etc.) for <math.h> functions. Ideally, we would have used iquantexp for the ones returning int and quantexp for the ones return decimal types. qexp won't work because it's used as the name of a function in statistics.

A different approach. We might define a function that returns the quantum as defined in IEC 60559: the value of a unit in the last position of the significand (i.e., 10^q where q is the quantum exponent). We could call the function quantum. The quantum exponent could be obtained by, for example, logbdN(quantumdN(arg)). Would a quantum function be more or less useful than the quantexp function?

-Jim