Re: Keyboard input

[mfeldman@seas.gwu.edu (Michael Feldman)]

In article <920031@hpclapd.HP.COM> defaria@hpclapd.HP.COM (Andy DeFaria) writes:
>>/ hpclapd:comp.lang.ada / sampson@cod.NOSC.MIL (Charles H. Sampson) /  4:20 pm  Sep 20, 1990 /
>
>Sure, sure, sure... But what if he Ada programmer, like the initial poster,
>*WANTS*  to  do  their own  single  character I/O   and handle any editting
>process,  perhaps   to provide  a different,   more  friendly or consistent
>editting process, huh?  How does he/she do it?
Actually, your PPS has the answer.
>
>P.S.	I hate when people don't answer the question posed
>P.S.S.	I'm  also not answering the  question but  I don't know the answer.
>	Perhaps the solution is  to call the OS  routine (read or getc) but
>	that isn't Ada or portable.
Indeed the solution is to call a routine from the operating system,
preferably by writing exactly the IO routine you need in C (for instance)
and making it Ada-callable by using pragma INTERFACE.

I'm not sure what you mean by "it isn't Ada or portable." If you mean that
it should have been included as a standard I/O package, you may be right;
I think I'd agree. But the fact is that is was _not_ included, and every
Text_IO implementation I'm aware of uses buffered input which requires a
CR to transmit the buffer contents. Some implementers have provided
additional I/O packages; some have not.

There are _lots_ of things that people could say should have been included
in the standard; undoubtedly your list would not be exactly the same list
as mine. That's the way it goes; the standard can't include everything in
the whole world. So we all cope by adding additional packages. If they
have to be written in another language and "pragma INTERFACE-d" to make
them Ada-callable, that is not sinful. Indeed, why else would this pragma
be in the language? At least the standard foresaw that OS services or
"foreign-language" programs would have to be called and provided the "hooks"
to do it. 

I would like very much to see a portable character-IO library -
portable in the sense that there would be an implementation-independent
package spec. The routine described by Rick Conn in a previous posting is
a good start in this direction. I will see if I have a copy and post it.
The package _body_ will necessarily be OS-dependent, because it's something
that can't be directly written in Ada.
---------------------------------------------------------------------------
Prof. Michael Feldman
Department of Electrical Engineering and Computer Science
The George Washington University
Washington, DC 20052
202-994-5253
mfeldman@seas.gwu.edu
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