Re: vector difference

utab <umut.tabak@xxxxxxxxx> wrote:

real :: a(4) = (/1.,2.,3.,4./)
real :: b(1) = (/2., 3./)

Presumably you mean b(2), but that's just a typo.

result is to be

res = (/1., 4./)

I wondered if there is a quick way to accomplish this through intrinsic
functions?

I'd say that "pack" and "any" are your friends. I'd probably do
something like

logical :: mask(size(a))
integer :: i
real, allocatable:: res

...
do i = 1 , size(a)
mask(i) = any(a(i)==b)
end do
res = pack(a,mask)

This assumes the f2003 feature of allocate-on-assignment. For a
pre-f2003 compiler, you'd need to add an

allocate(res(count(mask))

Those who play with this kind of thing a lot could probably put all that
into a single statement, possibly using spread, plus some dim arguments.
I sort of think I can see how to do that, but I always have a hard time
reading that kind of stuff. As a consequence, I pretty much never write
it and I'm loath to try on the fly here. I'd do the multi-step version
above.

As an aside, note that your problem definition seems to inherently be
based on exact comparisons of floatting point values. That is usually a
bad idea, but that is pretty much an independent question from this
array stuff. Change the arrays to, say, integer, and that objection
would go away.

--
Richard Maine | Good judgement comes from experience;
email: last name at domain . net | experience comes from bad judgement.
domain: summertriangle | -- Mark Twain
.

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