Implicit conversion integer <--> logical in Fortran if statement

Question

I have some legacy Fortran code which I was asked to analyze and translate to a modern language. I don\'t know which compiler was used in the past to compile the code, so fo

Answer 1

This is not possible in GFortran. The manual states:

However, there is no implicit conversion of INTEGER values in if-statements, nor of LOGICAL or INTEGER values in I/O operations.

You are only able to perform implicit conversions in assignments like your

  integer :: var
  var = .true.

but even there you must be very careful. It is not standard conforming and the value var will differ between compilers. Intel used to use -1 (all bits set to 1), unless -standard-semantics was chosen, for .true., but gfortran uses +1 as in the C language. New versions of Intel Fortran changes the default. The other direction is even trickier, there might be values which are neither .true. nor .false..