Align AnyMapTest, AnyArrayTest and with ElementTest

[line-o]

I always wondered why ElementTests for any element can be written as element() which is equivalent to element(*) but as map() and as array() are not permitted and always have to include the asterisk (map(*)) .

This is still the case even in XPath4 and I think we should have a look, if this can be omitted. It does not add any value IMHO, but maybe I am overlooking something important.

https://qt4cg.org/specifications/xquery-40/xquery-40.html#doc-xquery40-ElementTest https://qt4cg.org/specifications/xquery-40/xquery-40.html#doc-xquery40-ArrayTest https://qt4cg.org/specifications/xquery-40/xquery-40.html#doc-xquery40-MapTest

The "fix" would be as simple as

[255]   AnyMapTest   ::=  "map" "(" "*"? ")"

[265]   AnyArrayTest ::=  "array" "(" "*"? ")"

-- update after comment from @michaelhkay --

The same does not apply to FunctionTest as as function() specifies a zero-arity function wheras as function(*) matches functions of any arity.

[ChristianGruen]

Sounds reasonable to me. We should also allow fn() and function().

[michaelhkay]

Yes, I agree, this would be more logical.

[line-o]

I'll prepare a PR

[michaelhkay]

I don't think function() is a good idea because it's easily confused with function() as item()* which only matches a zero-arity function. It also introduces a potential ambiguity/incompatibility with things like "function() as function() as item()*"

[line-o]

I agree function() is different from function(*)

[line-o]

Sounds reasonable to me. We should also allow fn() and function().

@ChristianGruen Sadly, we cannot do that.

[line-o]

Do I read the EBNF for FunctionTests correctly, function() is only allowed in combination with the return type ("function" "(" ")" "as" SequenceType)?

https://qt4cg.org/specifications/xquery-40/xquery-40.html#prod-xquery40-FunctionTest

[251] FunctionTest ::= Annotation* ( AnyFunctionTest | TypedFunctionTest ) 
[252] AnyFunctionTest ::= ("function" | "fn") "(" "*" ")" 
[253] TypedFunctionTest ::= ("function" | "fn") "(" (SequenceType ("," SequenceType)*)? ")" "as" SequenceType

Shouldn't this be

[253] TypedFunctionTest ::= ("function" | "fn") "(" (SequenceType ("," SequenceType)*)? ")" ("as" SequenceType)?

[ChristianGruen]

@ChristianGruen Sadly, we cannot do that.

Just fine, makes sense, thanks.

[ChristianGruen]

Slightly off-topic: Hardly anyone seems to understand why some data types are prefixed (like xs:string), whereas others are not and look like function calls (like item()). Would it be too big a step to introduce prefixed alternatives, only followed by parentheses if the type is further refined?

Currently	Alternative
item()	xs:item
node()?	xs:node?
element(a)*	xs:element(a)*
map(*)+	xs:map+
map(xs:int, xs:item+)	xs:map(xs:int, xs:item+)
function(*)	xs:function
function() as xs:int	xs:function() as xs:int

If someone believes that my proposal is not just weird, I’ll be happy to create a separate issue for it.

[line-o]

Not sure how I feel about your idea @ChristianGruen. Trading three characters at the end with three characters at the beginning and having to educate users what this means when they see it in other people's code. Having all common types in one namespace seems valuable, though.

[michaelhkay]

function() is only allowed in combination with the return type ("function" "(" ")" "as" SequenceType)?

Correct. You can either omit all the types, so function(*) matches any function, or you have to include all the argument types AND the return type.

[michaelhkay]

item() vs xs:item

Having two ways of doing the same thing has the danger of creating more confusion; for the average reader, they'll assume these mean different things and have to go to the spec to find out that they don't.

In addition, it doesn't work for nodetests because these can be used in axis steps, for example child::text() which can't be replaced by child::xs:text, because xs:text is a valid element name.

[ChristianGruen]

Thanks. Yes, it’s too late for such fantasies.