[fpc-pascal] FORTRAN from FreePascal

Mark Morgan Lloyd markMLl.fpc-pascal at telemetry.co.uk
Sun Nov 19 10:43:23 CET 2017

On 19/11/17 04:00, Adriaan van Os wrote:
> Mark Morgan Lloyd wrote:> I think that conventional wisdom is that if 
> somebody's written numerical > analysis code you don't change it 
> gratuitously, since any alterations > will change rounding errors etc. 
> For some reason, that seems to apply > particularly to FORTRAN programs :-)
> The reason being explained here 
> <https://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/Floating_002dpoint-Errors.html> 

That obviously applies to all languages, I've never come across 
something which can represent 1/3 or pi exactly. But FORTRAN- or rather 
the way that people use it- has always seemed peculiarly sensitive, the 
classic problem being that recompiling with the optimising variant of 
the compiler produces significantly different results.

Elsewhere I came across discussion of (I think it was) a DEC FORTRAN 
compiler which produced the wrong results in a block of code only if it 
followed a comment. There's always been something grubby about FORTRAN 
compilers, and by now I find myself wondering whether people should even 
be attempting to design languages which don't compile easily (i.e. using 
recursive descent or whatever).

Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]

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