Re: Working around the limitations of SMIE

[Philip Kaludercic <philipk@posteo.net>]

Stefan Monnier via Users list for the GNU Emacs text editor
<help-gnu-emacs@gnu.org> writes:

>> I am writing a major mode for a little language I am using at
>> university, and wanted to try using SMIE for indentation and all the
>> other things.  The issue I find myself confronted with is that functions
>> are defined as in the following example:
>>
>>     func funktion(x : int): float
>>       x := x * x;
>>       return x;
>>     end
>>
>> where there is no delimiter between the return type (float), and the
>> rest of the body (such as "begin" or something like that).
>
> How is the separation between the function's return type and the
> function's body defined?  Is it based on the newline that follows the
> type, or is the language constrained to have types that are
> a single identifiers?

The latter.  This is the grammar production:

functionDeclaration: ' func ' identifier '( ' ( parameterDeclaration ( ', ' parameterDeclaration ) * ) ? ') '
    ( ': ' typeName ) ? block ' end ' ;

>> Another issue I ran into with the above definition is that instructions
>> are not indented correctly, as the above grammar doesn't express that in
>> this language doesn't expect a semicolon after an end (just like C
>> doesn't expect one after a "}").  So the result is that
>>
>> instead of:
>>
>>   while y >= y1 do
>>     dummy := zeile(x1, x2, xstep, y);
>>     y := y - ystep;
>>   end
>>   return 0;
>>
>> I get:
>>
>>   while y >= y1 do
>>     dummy := zeile(x1, x2, xstep, y);
>>     y := y - ystep;
>>   end
>>     return 0;
>
> Based on my experience, I suspect that the simplest solution for this is
> to make "end" return 2 tokens (the "end" and then a ghost ";").

Funnily enough I had tried this out too, but I must have messed up
somewhere because the result wasn't what I had intended.

Thanks.