Re: Scope of implicit none

Ron Shepard wrote:
In article <1inptgt.1ymor521v746f4N%nospam@xxxxxxxxxxxxx>,
nospam@xxxxxxxxxxxxx (Richard Maine) wrote:


Probably the single biggest blunder of the F90 committee was not to
make implicit none the default behavior.

It would have invalidated millions of lines of code, if they had.
So I guess there was little choice in that matter.

Sure there were other choices. One could also make arguments against
them, but to think that invalidating existing code would be the only way
to do this shows insufficient imagination.


I think compatibility with f77 was too important. If you remember, IMPLICIT NONE was not even allowed in f77, it would have been strange indeed to make something that was not even allowed in the current language the default in the next revision. That choice would not only have invalided those millions of lines of fixed-source code, but once the code was changed to make the IMPLICIT NONE explicit, it would have no longer been compatible with f77. Of course, because of the decade-long delay in approving the f90 standard (first by ISO, and only later by ANSI), many compilers did support IMPLICIT NONE as an extension, but as far as the language standardization process was concerned it would have been an
incompatible change, at least for fixed-source code.

I don't think I would have suggested it for fixed form source, only free form which was new at F90.


$.02 -Ron Shepard


--

Gary Scott
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Relevant Pages

  • Re: WG5-J3 Joint Meeting
    ... I like the idea of a subroutine interface "implicit none" ... Support the Original G95 Project: http://www.g95.org ... Support the GNU GFortran Project: http://gcc.gnu.org/fortran/index.html ...
    (comp.lang.fortran)
  • Re: Short records on unformatted reads
    ... implicit none ... Support the Original G95 Project: http://www.g95.org ... Support the GNU GFortran Project: http://gcc.gnu.org/fortran/index.html ...
    (comp.lang.fortran)
  • Re: Scope of implicit none
    ... It was a natural to introduce free form source with implicit none as the default. ... Support the Original G95 Project: http://www.g95.org ... Support the GNU GFortran Project: http://gcc.gnu.org/fortran/index.html ...
    (comp.lang.fortran)
  • Re: How to enable XEN in 2.6.23-rcS kernel?
    ... I did read, that Lguest and Xen was merged to upstream and must be in 2.6.23-rc1 kernel, but I can't see it in "make menuconfig". ... how to enable XEN support? ... Perhaps it would be clearer to make CONFIG_PARAVIRT implicit. ...
    (Linux-Kernel)
  • Re: Quick Summary of WG5/J3 London meeting
    ... or-ins library functions. ... I did quite a lot of bitmap image rasterization using the purdue bit intrinsic extensions with F77. ... Support the Original G95 Project: http://www.g95.org ... Support the GNU GFortran Project: http://gcc.gnu.org/fortran/index.html ...
    (comp.lang.fortran)