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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Reading a line of arbitrary length
Date: 1997/02/18
Message-ID: <dewar.856305993@merv>#1/1
X-Deja-AN: 219758407
References: <5ds40o$rpo@fg70.rz.uni-karlsruhe.de> <33032AE2.666F@mds.lmco.com>
 	<dewar.855848896@merv> <33037A74.44AF@mds.lmco.com> 	<dewar.855929857@merv>
 <3304D791.489C@acm.org> <dewar.855983270@merv> <JSA.97Feb16144316@alexandria>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-02-18T00:00:00+00:00
List-Id: <comp.lang.ada>


Jon said

<<That's impressive.  Too bad it won't be portable. :>>

As I mentioned before, our goal here is maximum functionality for GNAT
users. The unfortunate thing is the restrictions on the use of Access
being applied to nested procedures. These restrictions were considered
necessary during the design phase of Ada 95, to make it more practical
for compilers using displays (notably Alsys and RR) to implement access
to procedure.

For a compiler that uses static links, there is really no need to have
these restrictions, and that is why GNAT provides the attribute
Unrestricted_Access, which *can* be freely applied to procedures. 
The SPITBOL pattern matching stuff relies significantly on this
attribute, both at the implementation level and at the usage level.

The other important aspect of the implementation is some intimate
knowledge of the way Unbounded_String's are implemented in GNAT. This
is an efficiency issue, but a pretty important one!

Robert Dewar
Ada Core Technologies