log

[procedure] log z

R5RS, R6RS: Natural logarithm of z.

[procedure] log z1 z2

R6RS: Also has two-arguments version. Computes base-z2 logarithm of z1.

R6RS defines these boundary cases:

 (log +inf.0) => +inf.0
 (log 0.0)    => -inf.0
 (log 0)      => &assertion exception
 (log -inf.0) => +inf.0+πi
 (log -1.0+0.0i) => 0.0+πi
 (log -1.0-0.0i) => 0.0-πi  ;; if -0.0 is distinguished

See also exp, expt, log10.