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From: Paul Graham <pgraham@cadence.com>
Newsgroups: comp.lang.ada
Subject: Re: very specific question on Ada syntax
Date: Fri, 26 Jan 2001 11:17:06 -0500
Organization: Cadence Design Systems
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Date: 2001-01-26T11:17:06-05:00
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Mario Amado Alves wrote:
> 
> >    len := Color'image(Color'first)'length;
> 
> Yes, of course. Thanks. Just found an example in the RM itself:
> 
>   Rainbow'Base'First           4.1.4(16)
> 
> This was because I was wondering if a character literal could be tokenized
> without context. I guess not. In
> 
>   A'B'C
> 
> 'B' has the form of a character literal, but it is not it. I could perhaps
> rely on the fact (?) that there is no attribute of only one letter, but
> that is twisted to say the least.

VHDL, which is based on Ada, allows user defined attributes, so it is
possible to have, say

    x'some_user_attr'length

and there is no rule preventing a user defined attribute from being one
character
in length, so you can have:

    x'y'length

A VHDL parser won't get confused for the same reason that an Ada parser
wouldn't: a character literal cannot immediately follow an identifier.

Paul