Fortran (Was: The "does Python have variables?" debate)

[Gene Heskett]

On Tuesday 13 May 2014 01:48:43 Steven D'Aprano did opine
And Gene did reply:
> On Tue, 13 May 2014 00:33:47 -0500, Mark H Harris wrote:
> > there has to be a value add for scientists to move away from R or
> > Matlab, or from FORTRAN. Why go to the trouble?  FORTRAN works well
> > (its fast too), and there are zillions of lines of code cranking
> > away on huge linear arrays.  Enter Julia... over the next ten years;
> > seriously. Because of the value adds!
> > 
> >     Why?, glad you asked.  Enter self modifying code for one.
> 
> Self-modifying code is a nightmare inside the head of a Lovecraftian
> horror. There's a reason why almost the only people still using self-
> modifying code are virus writers, and the viruses they create are
> notorious for being buggy.

People who write buggy self-modifying code aren't paying attention. And 
you don't want those people anywhere near your code in 107% of the cases.

Stable, dead reliable self modifying code CAN be written, I have done it.  
And that code was still in use at the tv station that I wrote it for 15 
years later.  The only time it crashed was when there was a power failure, 
and the backup generator, which had to be started by hand, didn't get 
started soon enough to keep the battery backup, an old fried & dried 6 
volt gel-cell from running down.  An RCA 1802 device without an assembler 
even, just a hex monitor for code entry, and memory in those days (1980) 
was $400 for 4k of static ram when I built it.  By using self modifying 
code, I was able to do about 10k worth of code, using about 2.5k of that 
4k of ram.  Its all in how you reset each location that is modified on 
your way back to the top of the program to await the next command.

IMO, people who bad-mouth self-modifying code are folks who don't have the 
patience to do it right, because stable self-modifying code CAN most 
certainly be done.

Cheers, Gene
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