Re: Summing array elements

"Ron Shepard" <ron-shepard@[EMAIL PROTECTED]
> wrote in message 
news:ron-shepard-76B796.09441520042008@[EMAIL PROTECTED]
> In article <u0jm049f123f0c3ntnvi9dqbgo162dtvac@[EMAIL PROTECTED]
>,
> Luka Djigas <ldigas@[EMAIL PROTECTED]
> wrote:
>
>> Anyway, I read the help. But didn't manage to figure it out.
>> As far as I can see, sum can be used to summ an entire array in one or
>> more dimensions. How can one sum just some elements from, for example
>> one dimensional array ?
>
> Here is a description with examples:
>
>   http://gcc.gnu.org/onlinedocs/gfortran/SUM.html
>
> If you want a subset of an array, or you want a nonunit stride, then
> use the colon notation.
>
> $.02 -Ron Shepard

My compiler spits out an error here, Ron, and leaves me with warning 179 -

Comparing floating point quantities for equality may give misleading 
results.  mod has to have both types the same.  Mine were reals.  Yours
were 
ints, so it matters whether you compare to 2 or 2.0.  I think I get
reliable 
output for these data as real.

real :: a(50)

do  j=1, 50
  a(j) = real(j)
end do

s=0.
do 1 i=5,50
s=s+a(i)
1 continue

print *, SUM(a, MASK=MOD(a, 2.0)==1.0)


print *, s
end
output:
625.000
1265.00
, about half an dodd.
-- 
"A belief in a supernatural source of evil is not necessary; men alone
are quite capable of every wickedness."

~~  Joseph Conrad (1857-1924), novelist