Hey Nick, thank you very much. That sounds like a very good solution to my problem that does not require changes to org-mode.
Best Holger On Sat, Nov 19, 2011 at 5:00 AM, Nick Dokos <nicholas.do...@hp.com> wrote: > Holger Hoefling <hhoef...@gmail.com> wrote: > > > I think you misunderstood me there - I am actually not worried about how > > computationally intensive the tangling process is. This always works very > > quickly, so even if they have to be copied around and take a bit longer, > I > > would not mind. > > > > Ah, ok - so you are talking about > > tangle compile > org -------> bunch of files -------------> output > > The tangling step produces a bunch of files that are (re)compiled (or in > any case require some sort of lengthy processing) to produce some output > file. > > > IMO, the best way to deal with it is still make: let's say > > foo.org ----> a.x b.x c.x ------> foo.out > > where the first arrow is the tangle and the second arrow is some > processor, call it X. > The standard way to set up a makefile is schematically: > > --8<---------------cut here---------------start------------->8--- > foo.out: a.x b.x c.x > X a.x b.c c.x -o foo.out > > a.x b.x c.x: foo.org > tangle foo.org > > --8<---------------cut here---------------end--------------->8--- > > > Rewrite the make file as follows: > > > --8<---------------cut here---------------start------------->8--- > foo.out: a.y b.y c.y > X a.y b.y c.y -o foo.out > > a.y: a.x > cmp --silent a.x a.y || cp a.x a.y > > b.y: b.x > cmp --silent b.x b.y || cp b.x b.y > > c.y: c.x > cmp --silent c.x c.y || cp c.x c.y > > a.x b.x c.x: foo.org > tangle foo.org > --8<---------------cut here---------------end--------------->8--- > > > So if the *contents* of (say) a.x have not changed by the tangling, it > compares > equal to a.y and the copy is skipped. That leaves a.y untouched. > > OTOH, if the contents of a.x change (or a.y does not exist in the first > place), the comparison fails and we copy a.x to a.y. That updates a.y > and forces further updates on anything that depends on it. > > Using some make fu (works for GNU make, but not necessarily for other > makes), > you can write it more compactly: > > > --8<---------------cut here---------------start------------->8--- > foo.out: a.y b.y c.y > X a.y b.y c.y -o foo.out > > %.y: %.x > -cmp --silent $< $@ || cp $< $@ > > a.x b.x c.x: foo.org > tangle foo.org > --8<---------------cut here---------------end--------------->8--- > > HTH, > Nick > > >
