if (int x=..) but no while(int x=..) ?

[kellywilson at nowhere.com]

Hey Kyle and Lionello,

In article <dv8b3l$2109$4 at digitaldaemon.com>, Kyle Furlong says...
>
>Lionello Lunesu wrote:
>> I like the fact that we can do
>> 
>> # if (int recvd = ts.receive(buffer)) {...}
>> 
>> but is there any reason why this shouldn't apply to "while" also?
>> 
>> # while (int recvd = ts.receive(buffer)) {...}
>> 
>> main.d(26): found 'recvd' when expecting '.' following 'int'
>> main.d(26): found '=' when expecting identifier following 'int.'
>> main.d(26): found 'ts' when expecting ')'
>> main.d(26): found ')' when expecting ';' following 'statement' 
>> 
>> 
>
>Seems an obvious next step, are there any drawbacks that people can think of?


PLEASE read the CAVEAT at the end of the post concerning the following rule!

The grammar for D does not allow a 

"Declarator = Expression"

inside the braces of a while statement. The "IfCondition" rule does allow this
for the if statements, however. Now, can the grammar be modified to accept the
"Declarator = Expression" rule? Yes, I just modified my grammar and it works
without conflicts. As for any deeper questions about the
validity/usability/maintainability of this...well that is for Walter to decide,
I guess.

By the way:

Each of the "IfStatement"/"WhileStatement"/"DoStatement" rules are explained
with the following in the documentation:

"Expression is evaluated and must have a type that can be converted to a
boolean."

This would seem to indicate that each of these constructs can use the
"Declarator = Expression" rule I mentioned above.

Thanks,
Kelly Wilson 

CAVEAT:::: The rule "Declarator = Expression" should ACTUALLY read "Basic_Type
Declarator = Expression". The dmd frontend (version 0.149) uses this rule
instead of the rule I keep quoting above....I just didn't want to confuse anyone
following along in the documentation online. I also use the "Basic_Type...."
rule as the Basic_Type is needed before Declarator.