dtc expressions

[Stephen Warren]

On 03/15/2012 06:29 PM, David Gibson wrote:
> On Wed, Mar 14, 2012 at 09:40:13AM -0600, Stephen Warren wrote:
>> On 03/14/2012 08:46 AM, David Gibson wrote:
>>> So, in order to actually make progress on the dtc expressions / macros
>>> / whatnot stuff, I really think I should dust off my integer (constant)
>>> expressions patch, and we can apply that.
>>>
>>> While we still have disagreements on a bunch of stuff here, I think
>>> we're at least agreed on what integer expressions should look like.
>>> And even if we change approaches later (e.g. to your ifs and fors in
>>> dtc approach) the integer expression syntax won't change, only the
>>> implementation.
>>
>> I'd love to see something like that. I've don't think I've actually
>> looked through your patches for that yet; I briefly looked at Jon's
>> since they're in a branch in the dtc repo, but I don't think I managed
>> to track down the patches you sent for this.
> 
> It was quite a while back that I posted.  I've got a version below,
> but it's *very* bitrotted and won't even go close to applying at
> present.  I'm meaning to update it, but it will take a little time.

That looks like a good set of integer expressions.

Do you think it'd be easy to agree on a simple "#define foo (expr)"-like
syntax on top of this? I think that'd cover a lot of the use-cases
people are looking for right now, which are more about
creating/naming/using constants rather than building whole nodes or
properties in some programmatic way.

> Index: dtc/dtc-lexer.l
...
> +<*>"<<"		{ return DT_LSHIFT; };
> +<*>">>"		{ return DT_RSHIFT; };
> +<*>"<="		{ return DT_LE; };
> +<*>">="		{ return DT_GE; };
> +<*>"=="		{ return DT_EQ; };
> +<*>"!="		{ return DT_NE; };
> +<*>"&&"		{ return DT_AND; };
> +<*>"||"		{ return DT_OR; };

For my education, why aren't all the operators in the lexer file? When I
first looked at this file, it seemed like a bunch were missing because
they're only represented in the parser, as literal strings.