No parenthesis for assert?

[Stewart Gordon]

On 12/01/2012 22:56, Alex Rønne Petersen wrote:
> On 12-01-2012 22:35, Peter Alexander wrote:
<snip>
>> Not to mention that it would be ambiguous with the comma operator:
>>
>> assert (a, b); // is this the comma operator, or two arguments?
>
> I did point out that it would only really make sense for asserts without messages.

Therein lies the point.  If we changed the AssertExpression grammar to

AssertExpression:
     assert ( AssignExpression )
     assert ( AssignExpression , AssignExpression )
     assert AssignExpression

then the form

     assert ( AssignExpression , AssignExpression )

would become ambiguous, because it could be parsed as

     assert ( AssignExpression , CommaExpression )
     assert ( CommaExpression )
     assert ( Expression )
     assert AssignExpression

In some cases it's resolved by an "if it's parseable as X, it's X" rule, but this would 
create fragility because of the possibility of a CommaExpression of three or more terms. 
As such, it would be a case of explicitly disallowing

     assert ( CommaExpression )

in the grammar.

Stewart.