Re: Voyager (2nd Edition)

From: [at]} <Rex>
Date: Wed, 17 Mar 2004 10:06:34 -0600

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        This subject has gotten far from CP and Black Box, so many of you may want to skip this message. Hector has forwarded some comments about FORTRAN that I believe are misleading, and I feel compelled to respond. Please note that I receive only the Black Box digest, so I may be far behind the discussion at the time of this message.

        The assertion is that
DO 20 I=1,100
could be mistyped as
DO20I=1.100
and interpreted by the compiler as an assignment statement instead of the intended DO loop. While such an error is possible, it is worth pointing out that it would require a specific combination of three typing errors, any one of which should be noticed by the programmer. If any one of the three errors is missing, the program would generate a compiler error. How many languages do you know that will give the correct result if you make three typing errors?

        In addition, the error is easily avoided with the statement IMPLICIT NONE, which has been available and known to FORTRAN programmers and encouraged for at least 20 years. The IMPLICIT NONE statement requires that all variables be explicitly declared, thereby catching many such typing errors.

        Readers may also have an exaggerated notion of FORTRAN as an archaic language. Although it was around for decades before the Pascal or C language families, it has been modernized. Most of the former deficiencies have been eliminated or deprecated, and it is still probably unequaled for numerical programming. Even the infamous source code line format is now deprecated. Because such features as triangular matrices and direct matrix manipulation are part of the language, optimization is easy. I started programming with FORTRAN 66 (from 1966), which was the successor to FORTRAN IV. Even then it was trivial to pass a multidimensional open array (with size unknown at compile time) to a subroutine (i.e., procedure). Most modern languages got this capability only recently, if at all. Even today, if I am not mistaken, it is not possible in some of the Oberon languages.

        Finally, it is my understanding that the Mars Rover software was written in Java, not FORTRAN. I saw one claim on the Internet (which I cannot verify) that the operating system (which was written in an unspecified language) has a tendency to reboot in a loop after certain CompactFlash errors, which is apparently exactly what happened.

Sincerely,
Rex Couture
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Received on Wed Mar 17 2004 - 17:06:34 UTC