exp versus expt

[Kent Dybvig <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>]

We have a way to find an exponent of e (exp n) and of an arbitrary
base (expt b n).  We have a function to find the log base e (log n)
but not the log in an arbitrary base.  How about adding (log n b)?

Why do we have (expt b n)?  We could instead give exp an optional
argument specifying the base, i.e., (expt b n) => (exp n b).  Why
is it not done this way in Common Lisp, as it is for log?  Perhaps
because the argument order would seem backwards?

Kent