I have an array of strings in a Fortran program. Not a single character string. I know that one of the values in the array is "foo". I want to know the index of the array that contains "foo". Is there a way to find the index other than a brute force loop? I obviously can't use the "minloc" routine since I'm not dealing with numerics here. Again, just to make sure: I am not searching for a substring in a string. I am searching for a string in an array of strings.
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2 Answers
implicit none
integer i
character*8 a(100)
do i = 1,100
a(i)='foo'
enddo
a(42)='bar'
call f(a,len(a(1)),shape(a)*len(a(1)),'bar ')
end
subroutine f(c,n,all,s)
implicit none
integer n,all
character*(*) s
character*(all) c
write(*,*)index(c,s)/n+1
end
a.out -> 42
note this code is treating the entire array as one big string and searching for substrings so it will also find matches that are not aligned with the component string boundaries.
eg. a false match occurs with adjacent entries such as:
a(2)='xxbar '
a(3)=' yyy'
Some additional work required to ensure you find an index that is an integer multiple of n ( of course by the time you do that a simple loop might look preferable )
1 Comment
francescalus
For the "additional work", you presumably mean to handle something like
call f(['fob','arb','bar'], 3, 9, 'bar')? [There's an argument missing in your call.]Well, after thinking about it, I came up with this. It works if "foo" is known to be either absent from the array, or located in one and only one place:
character(len=3) :: tags(100)
integer :: test(100)
integer :: str_location
! populate "tags" however needed. Then search for "foo":
test=(/(i,i=1,100)/)
where (tags.ne."foo") test=0
str_location = sum(test)
I am guessing this is actually slower than the brute force loop, but it makes for compact code. I thought about filling "test" with ones and using maxloc, but that doesn't account for the possibility of "foo" be absent from the array. Opinions?
1 Comment
francescalus
If you want "compact" in the absence of
findloc then minval(pack([(i,i=1,100)],tags.eq.'foo')). But that's not really a good way.
findlocworks on character arrays? [It isn't F90 and isn't widely implemented.]