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Thread: Clean up optional rules in grammar

Clean up optional rules in grammar

From
Peter Eisentraut
Date:
There are a number of rules like this in the grammar:

opt_foo: FOO
         | /*EMPTY*/
;

And there are some like this:

opt_foo: FOO         {}
         | /*EMPTY*/  {}
;

and some even like this:

%type <node> opt_foo

opt_foo: FOO         { $$ = NULL; }
         | /*EMPTY*/  { $$ = NULL; }
;

(I mean here specifically those rules where FOO is a noise word and the 
actions are the same in each branch.)

It's obviously confusing to have multiple different styles to do the 
same thing.  And these extra rules (including the empty ones) also end 
up in the output, so they create more work down the line.

The attached patch cleans this up to make them all look like the first 
style.
Attachment

Re: Clean up optional rules in grammar

From
Heikki Linnakangas
Date:
On 11/11/2020 11:12, Peter Eisentraut wrote:
> The attached patch cleans this up to make them all look like the first
> style.

+1

- Heikki

Re: Clean up optional rules in grammar

From
Vik Fearing
Date:
On 11/11/20 10:12 AM, Peter Eisentraut wrote:
> There are a number of rules like this in the grammar:
> 
> opt_foo: FOO
>         | /*EMPTY*/
> ;
> 
> And there are some like this:
> 
> opt_foo: FOO         {}
>         | /*EMPTY*/  {}
> ;
> 
> and some even like this:
> 
> %type <node> opt_foo
> 
> opt_foo: FOO         { $$ = NULL; }
>         | /*EMPTY*/  { $$ = NULL; }
> ;
> 
> (I mean here specifically those rules where FOO is a noise word and the
> actions are the same in each branch.)
> 
> It's obviously confusing to have multiple different styles to do the
> same thing.  And these extra rules (including the empty ones) also end
> up in the output, so they create more work down the line.
> 
> The attached patch cleans this up to make them all look like the first
> style.

No objections, but could we also take this opportunity to standardize
the comment itself?  Even in your patch there is a mix of spacing and
casing.

My preference is /* EMPTY */.  That is, uppercase with spaces, but
whatever gets chosen is fine with me.
-- 
Vik Fearing

Re: Clean up optional rules in grammar

From
Peter Eisentraut
Date:
On 2020-11-11 12:43, Vik Fearing wrote:
> No objections, but could we also take this opportunity to standardize
> the comment itself?  Even in your patch there is a mix of spacing and
> casing.
> 
> My preference is /* EMPTY */.  That is, uppercase with spaces, but
> whatever gets chosen is fine with me.

Looks like /*EMPTY*/ is the most common right now.  I agree this should 
be straightened out.

Re: Clean up optional rules in grammar

From
John Naylor
Date:

On Wed, Nov 11, 2020 at 5:13 AM Peter Eisentraut <peter.eisentraut@enterprisedb.com> wrote:
It's obviously confusing to have multiple different styles to do the
same thing.  And these extra rules (including the empty ones) also end
up in the output, so they create more work down the line.

The attached patch cleans this up to make them all look like the first
style.

+1 for standardizing in this area. It's worth noting that Bison 3.0 introduced %empty for this situation, which is self-documenting. Until we get there, this is a good step.

--
John Naylor
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company 

Re: Clean up optional rules in grammar

From
Peter Eisentraut
Date:
On 2020-11-11 11:54, Heikki Linnakangas wrote:
> On 11/11/2020 11:12, Peter Eisentraut wrote:
>> The attached patch cleans this up to make them all look like the first
>> style.
> 
> +1

done