[xquery-talk] incorrect syntax?

[Michael Sokolov]

Sorry, I think I neglected to include a let before a couple of the 
returns.  But my main point was the unusual (and probably unfamiliar to 
people used to other languages) change in the interpretation of 
parentheses when they follow the return keyword and when they follow the 
return function.

Admittedly the idea of defining a function with the same name as a 
keyword is contrived and ill-advised, right up there with C++ operator 
overloading.  It just occurred to me on reading Michael Kay's comment 
'There is no function called "return"' that there actually could be one.

Mike Sokolov

On 10/1/2012 8:55 PM, Ronald Bourret wrote:
> This is actually very straightforward. "return" is a keyword, used in 
> FLWOR expressions and a few other places. There is no standalone 
> "return" in XQuery. Thus:
>
>    let $x:=0 return (23)
>
> is a valid (if uninteresting) FLWOR expression that is equivalent to 
> the even less interesting (but still valid) expression:
>
>    (23)
>
> And a standalone "return" is illegal:
>
>    return (23) (: error :)
>
> Where you have included parentheses below, you are calling a function 
> named "return" and XQuery works as expected. It's a bad idea to name a 
> function using a keyword as a name, but XQuery allows it. If you 
> replace "return(...)" with "foo(...)" in the expressions below, the 
> intended meaning will be clear.
>
> The last two XQuery expressions should return errors (and do in the 
> online Zorba XQuery processor I tried them in). As noted above, this 
> is because there is no standalone use of the "return" keyword -- 
> either the processor you are using has a bug or you haven't shown us 
> the entire expression.
>
> Thanks,
>
> -- Ron
>
> On 10/1/2012 5:34 PM, Michael Sokolov wrote:
>> On 10/1/2012 10:48 AM, Michael Kay wrote:
>>> There is no function called "return". Just remove the keyword.
>>> Depending on the context, you might need to remove the outer curly
>>> braces as well.
>>>
>>> It's a little confusing because you can say
>>>
>>> let $x:=0 return 23
>>>
>>> but you can't say
>>>
>>> return 23
>>
>> Actually if you really start to dig, it becomes a lot confusing
>>
>> you can say
>>
>> let $x := 0 return (23)
>>
>> but in that instance return is not a function call; the parentheses here
>> are constructing a sequence (of one item)
>>
>> But if you say
>>
>> declare default function namespace "x";
>> declare function return ($x) { $x+1 };
>> return (23)
>>
>> that does seem to return 24 for at least one processor that I tried,
>> which seems truly bizarre (to me, anyway)
>>
>> yet
>>
>> declare default function namespace "x";
>> declare function return ($x) { $x+1 };
>> return 23
>>
>> returns 23
>>
>> while
>>
>> declare default function namespace "x";
>> declare function return ($x) { $x+1 };
>> return return(23)
>>
>> returns 24
>>
>> -Mike Sokolov
>>
>>
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