On 2016-12-08 16:31, Stefan Monnier wrote:
> Indeed.  But the Elisp interpreter is slow compared to the `format`
> parser, so I'd expect the use of a single `format` call to be more
> efficient (both in code size and execution time).  That's just a gut
> feeling, tho, I have no hard data to back it up (my implementation uses
> a single `format` call partly because of that gut feeling but also
> because it seemed easier).

Indeed, format seems to be a bit faster:

(benchmark-run-compiled 50000 (let ((a 1) (b 2))
                                (fmt "What's $a + $b? About $(+ a b).")))
=> (1.4476880189999999 2 0.11585387999999952)

(benchmark-run-compiled 50000 (let ((a 1) (b 2))
                                (format "What's %s + %s? About %s." a b (+ a b))))
=> (1.332636799 1 0.057698191000000065)