g77.info: Fortran 90

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Fortran 90

   The GNU Fortran language includes a number of features that are part
of Fortran 90, even when the `-ff90' option is not specified.  The
features enabled by `-ff90' are intended to be those that, when `-ff90'
is not specified, would have another meaning to `g77'--usually meaning
something invalid in the GNU Fortran language.

   So, the purpose of `-ff90' is not to specify whether `g77' is to
gratuitously reject Fortran 90 constructs.  The `-pedantic' option
specified with `-fno-f90' is intended to do that, although its
implementation is certainly incomplete at this point.

   When `-ff90' is specified:

   * The type of `REAL(EXPR)' and `AIMAG(EXPR)', where EXPR is
     `COMPLEX' type, is the same type as the real part of EXPR.

     For example, assuming `Z' is type `COMPLEX(KIND=2)', `REAL(Z)'
     would return a value of type `REAL(KIND=2)', not of type
     `REAL(KIND=1)', since `-ff90' is specified.