grouping a flat list of number by range

[joh12005 at yahoo.fr]

hello,

i'm looking for a way to have a list of number grouped by consecutive
interval, after a search, for example :

[3, 6, 7, 8, 12, 13, 15]

=>

[[3, 4], [6,9], [12, 14], [15, 16]]

(6, not following 3, so 3 => [3:4] ; 7, 8 following 6 so 6, 7, 8 =>
[6:9], and so on)

i was able to to it without generators/yield but i think it could be
better with them, may be do you an idea?

best regards,

J.