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Subject: Re: [boost] [proto] grammar compile error
From: Felipe Magno de Almeida (felipe.m.almeida_at_[hidden])
Date: 2009-07-04 13:41:15

On Sat, Jul 4, 2009 at 2:29 PM, Eric Niebler<eric_at_[hidden]> wrote:
> Felipe Magno de Almeida wrote:
>> And I want to create the looser grammar, composed of all
>> sub-expressions inside the full grammar somehow. Is there a way to do
>> this in proto, or should I start creating it with mpl?
>> Is there a way to iterate a grammar?
> This sounds like more work than is truly necessary. There is really only one
> good reason to specify a grammar when defining a domain, and that is to
> disable troublesome operator overloads.
> My suggestion would be to not
> specify your dsel's grammar up front, but rather only validate full
> expressions at the point of evaluation. You lose no safety that way.

Defining a grammar loosely is harder than specifying it fully.
Doing it fully, all I need to do is: shift(create, table, table_name,
columns) and I'm done.
But if I do it for all partial expressions, I might forget something.
I'm trying to define a SQL grammar. Having it checked earlier, helps
me traversing it later, since I know it is right. Also, it prohibits
most expressions right away, giving better error messages. I wouldn't
have to check later on if there's a non-sensical terminal anywhere.

create << table << create would have no overloads.

All I need is to traverse a grammar, and define another grammar with
all sub-expressions.
Since the grammar is not very big, it shouldn't be too hard on the
compiler (I hope).
Though I'm not very experienced with proto yet.

Is transforming a grammar a really difficult task?

> --
> Eric Niebler
> BoostPro Computing

Felipe Magno de Almeida

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