Fortran list directed input reading logical variables

Fortran 90’s list directed input is powerful, flexible, but tricky. My function to read a keyword, boolean value pair from a file was not working when I reshuffled the order of the input parameters (blame Python’s orderless dictionaries for this, not that I’m complaining). Originally I just read the string and logical straight in, then tested the string for a match to the key. However when reading list directed logicals it seems that fortran was biting off the next record as well. New improved read_bool follows:

subroutine read_bool(iunit,key,val)
! Searches the input file for the key and reads the value
! to the supplied variable when it finds it.
implicit none
integer iunit
character (len=20) :: st
character (len=*) :: key
logical :: val
integer i,w
w = len(key)
do while (st(1:len(key)) .ne. key)
print *,'reading value'
read(iunit,*,iostat=i) st
print *,i
print *,st,val
! print *,key,st(1:len(key)),i
if(i .eq. -1) then
write(*,*) key
stop 'fatal error: parameter not found'
if (st(1:len(key)) .eq. key) then
! print *,'I found ',st
read(iunit,*,iostat=i) st,val
write(*,*) st,val
end subroutine read_bool

Respect to Nick Maclaren for his online powerpoint slides (which didn’t lead me to the answer, but were quite useful nonetheless.) Also see, and the QUB notes which I always seem to stumble back to.


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