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From: gast@ucla-cs.ARPA (David Gast)
Newsgroups: net.lang.f77
Subject: Re: f77 bug:  comparing logicals
Message-ID: <12846@ucla-cs.ARPA>
Date: Wed, 7-May-86 22:28:27 EDT
Article-I.D.: ucla-cs.12846
Posted: Wed May  7 22:28:27 1986
Date-Received: Sun, 11-May-86 03:33:01 EDT
References: <464@cubsvax.UUCP>
Reply-To: gast@ucla-cs.UUCP (David Gast)
Organization: UCLA Computer Science Dept.
Lines: 43

In article <464@cubsvax.UUCP> peters@cubsvax.UUCP (Peter S. Shenkin) writes:
>The following program, compiled with f77, prints "f" for all three
>comparisons;  under VMS, using dec fortran,  the three results are
>"T", "F" and "T", as one would expect.
>
>cccccccccccccccccccccccc BEGIN HERE ccccccccccccccccccccccccccccccccccccccc
>	write(6,*)'.true. .eq. .true. :', .true. .eq. .true.
>	write(6,*)'.true. .eq. .false. :', .true. .eq. .false.
>	write(6,*)'.false. .eq. .false. :', .false. .eq. .false.
>
>	stop
>	end
>cccccccccccccccccccccccc END HERE cccccccccccccccccccccccccccccccccccccccccc


When will you guys learn?  The way to figure out what the language requires
is not to write a program and see what the compiler does, but to read the
language definition and see what is required.  Surely, by now, you must have
all seen some program where the compiler makes a mistake.  For those of you
who are blind, the example at hand will suffice.

Not relying on the compiler is particularly true for FORTRAN.  In the first
place, F77 looks a lot like its older brothers, but its semantics are quite
different.  For example, boolean short circuit evaluation is permitted, but 
not required.  Second, no matter what the compiler manual says, the compiler 
does not enforce the F77 standard (or the earlier ones).  This statement
applies to the UN*X F77 compiler and to the IBM VFORTRAN compiler, for
example.  (The IBM manual also contains statements which are blatantly
incorrect, as well).  Perhaps some day, I will post a F77 program that 
has an error on almost every line--the compilers and the run-time system 
do not catch or flag or warn about any of them.

Now to the example at hand.  F77 does not allow the .eq. operator
between logicals.  There is a syntax error not detected by the 
compiler. Isn't FORTRAN a great language?

If you are tired of crap like this, I suggest you throw your FORTRAN
compiler out, and get an ALGOL 68 compiler.  You won't even have to
worry about unitialized values.  And who knows, your program might
actually even work.

David Gast
gast@CS.UCLA.EDU