[antlr-interest] Re: on parsers look and feel

[micheal_jor]

--- In antlr-interest at yahoogroups.com, Cristian Amitroaie
<cristian at a...> wrote:
> Hello guys,
> 
> Case:
>    o sometimes I kind of foreget what name I gave to the "=" token
from the 
> Lexer (EQ/EQUAL/EQUALS/ASSIGN) when I want to add a new rule to a
parser.
>    o sometimes I get bored to write LCURLEY instead of "{" or '{'
>    o sometimes it's hard for me to follow rules full of SEMI,
LCURL(E)?Y, 
> LBRACK, LPARENS and so on
> 
> For example, I would like to see my parser rules look like:
> 
> assign:
>         ID "="^ ID ";"!
>     ;

<SNIP>

> Are there any disadvantages/risks related to this approach?

<SNIP>

> Or it's just a matter of taste?

Christian,

It might be a taste thing but, there is a difference between a
character (or indeed sequence of characters i.e. string) literal and a
token. The same character/string literal can result in a different
token depending on where/when it appears in the lexers input stream.

Using character/string literals directly in parser/treeparser grammars
can result in a loss of clarity since it is possible that the same
literal repeated in a grammar actually means different things. Quite
apart from the technical issue of how well ANTLR supports the use of
character/string literals is the issue of how well our grammars convey
their intent. They should be designed to be easy to comprehend and
maintain after all.

Ric's idea of adopting a standard "template" and growing from there is
right on the ball IMO.

Cheers,

Micheal
ANTLR/C#



 

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