Re: typed pipes

["Björn Persson" <spam-away@nowhere.nil>]

Jacob Sparre Andersen wrote:

> I am not sure if I would want the system to _force_ both ends of the
> pipe to agree, but I would definitely want the reading end to be
> _informed_ of what the writing end is doing.
> 
> But doing the Unchecked_Conversion once the data are inside the
> reading process is probably the correct solution.
> 
> This could probably not be done on the shell level, since pipes are an
> operating system feature, and not just a shell feature.

No, it definitely couldn't be done in a Unix shell. It would require very
deep changes to how the kernel handles files, including changes to the
system calls. And if you had it for pipes you'd want it for disk files too,
which would affect the filesystems. I suspect that the resulting operating
system would be almost, but not quite, entirely unlike Unix.

And how could you make it work for all programming languages? Types are very
much a programming language concept. I suppose you could design it so that
an Ada program could communicate "type File_Record is -18 .. 7000;" to
another Ada program, while a C program would see "int16_t", but how would
you explain tagged types, discriminants and stuff to C? And then there are
other languages with types that can't be expressed in Ada.

-- 
Bj�rn Persson                              PGP key A88682FD
                   omb jor ers @sv ge.
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