https://github.com/chrisdone/number.git
git clone 'git://github.com/chrisdone/number.git'
Do trivial arithmetic on the numbers at point. Attempts to preserve padding when it can. Examples:
M-x number/add 1 RET
1 -> 2
05 -> 06
6.30 -> 7.30
07.30 -> 08.30
-08.30 -> -07.30
M-x number/pad 2 RET
5 -> 05
M-x number/pad 2 RET 6 RET
3.141 -> 03.141000
The “guessing” where the number is isn't yet quite awesome, e.g. it
doesn't know that the 05 in 2014-05-01 is a month and not,
e.g. the number -05. But you can use the region to explicitly denote
the start and end of the number.
The following keybindings might be nice to use:
(global-set-key (kbd "C-c C-+") 'number/add)
(global-set-key (kbd "C-c C--") 'number/sub)
(global-set-key (kbd "C-c C-*") 'number/multiply)
(global-set-key (kbd "C-c C-/") 'number/divide)
(global-set-key (kbd "C-c C-0") 'number/pad)
(global-set-key (kbd "C-c C-=") 'number/eval)