lisp timestamp

In [[Emacs Lisp]] at least, times are stored as lists like so:

'(24814 288)

in the form of (ticks . hz). If hz is 1000000000 (that’s \(1^{10}\)), this represents a nanosecond resolution clock.

Alternatively, if it’s a list of four elements, like so:

'(24814 232 507836 148000)

This represents (high low micro pico), which, in seconds, can be represented as:

\(high * 2^{16} + low + micro * 10^{-6} + pico * 10^{-12}\)

or, as an [[s-expression]]:

(defun calc-time (high low micro pico)
  (+ (* high (expt 2 16)) low (* micro (expt 10 -6)) (* pico (expt 10 -12))))

(let* ((now (current-time))
       (float-time-from-now (float-time now))
       (calc-time-from-now (apply 'calc-time now)))
  (message "float-time\t%s\ncalc-time\t%s" float-time-from-now calc-time-from-now))