Re: Get_Immediate warning, (was: How to get a character?)

[Robert Dewar <robert_dewar@my-dejanews.com>]

In article <87hfqkgnrm.fsf@bglbv.my-dejanews.com>,
  bglbv@my-dejanews.com wrote:

> The standard is clearly written under the assumption that
> interactive input isn't normally buffered more than one
> line at a time, but this doesn't seem to be even an
> Implementation Advice, much less a requirement.

That's quite wrong.

The standard is written under the assumption that Text_IO
is reading and writing files. Well more accurately, the
Ada 83 standard is written that way, and the Ada 95
standard copies the definitions, adding only Flush and
Get_Immediate, both of which are pretty much completely
implementation dependent.

The entire issue of applying Text_IO to "interactive I/O"
(whatever that may be, this is not a technical term), is
in fact implementation dependent.

If you try to do a VERY accurate implementation of Text_IO
on interactive terminals, you sometimes have to press
Line return twice, since you need to be sure there is no
page mark in the input before you know exactly what is
going on.

Most reasonable Ada compilers do something about this (e.g.
GNAT defines that there are no page marks for non regular
files), but this is definitely in the implementation
dependent area.

Basically the design approach was that Text_IO is to be
used for simple I/O with no fancy requirements (sort of
like DISPLAY and ACCEPT in COBOL). The assumption (even
more true in these windowed days) is that any serious I/O
will be done with packages at a completely different level
in any case.

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