Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!lanl!lambda!jlg
From: jlg@lambda.UUCP (Jim Giles)
Newsgroups: comp.lang.misc
Subject: Re: Cheap implementations of languages (Re: Pointers and poor implementations (was: Re: JLG's flogging ...))
Message-ID: <14323@lambda.UUCP>
Date: 10 Apr 90 20:20:23 GMT
References: <5486@ganymede.inmos.co.uk>
Lines: 29

From article <5486@ganymede.inmos.co.uk>, by mph@lion.inmos.co.uk (Mike Harrison):
> [...]
> While I think that your comparison is fair, you have missed out some tricky 
> bits of Fortran, which *might* change the perspective.
> For example:
>   - DATA statements, with implied DO, which can be quite complex when you 
>     have nested cases.

Why should these be any harder to implement than nested run-time loops?
Actually, I've implemented a parser for do-loop style data initialization
for an I/O library.  It was not particularly difficult.

> [...]
>   - EQUIVALENCE statements, which (given overlapping EQUIVALENCEd arrays) can 
>     set up quite complex constraint problems.

Equivalence is about as difficult (or easy) to implement as C's untagged
unions are.  At least with respect to constraint problems, the two features
are nearly identical.  After all, C also has to anticipate that arrays
might be aliased in an overlapping fashion through the union construct.

When comparing languages, one must have an eye for what features are
really correspondent.  For the most part, procedural languages tend
to all have pretty much the same features.  From a human perspective
these language features may _seem_ vastly different in form and
convenience.  From the compiler's perspective, they are all just
about the same.

J. Giles