internal/number: simplify scientific formatting

Simplify computation of exp.
Makes it easier to understand and more
clearly correct. Comma already determines
the position of the comma, so no need to
thinker with the exponent.

Change-Id: I969326e9453d88eff4db96b793349f9c951865e3
Reviewed-on: https://go-review.googlesource.com/58912
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
2 files changed