[xquery-talk] Fuctions and variables in replacement string of fn:replace()

[Liam R E Quin]

On Tue, 2013-04-30 at 23:01 -0400, David Sewell wrote:
> When using fn:replace(), is it kosher or illegal to construct the
> replacement string dynamically using a function? In some cases this
> seems to work (tested in Saxon and MarkLogic):
> 
> xquery version "1.0";
> let $string := "Now, let's SEND OUT for QUICHE!!"
> let $match := "[A-Z][A-Z]+"
> return replace($string, $match, concat("$0","$0"))
> ==> Now, let's SENDSEND OUTOUT for QUICHEQUICHE!!
> 
> but in other cases it doesn't. For example, lower-case("$0") has no
> effect. And substring("$0", 1, 1) throws an error.

In your first example,
return replace($string, $match, concat("$0","$0"))
the replace function gets called with 3 arguments:
    replace(
      "Now, let's SEND OUT for QUICHE!!",
      "[A-Z][A-Z]+",
      "$0$0"
    )

Now, replace() treats $0 as whatever matched - it is not a variable
reference, even though it looks like one. Th $ sign is special to
replace().

However, lower-case("$0") will return "$0" since neither $ nor 0 is an
upper case letter.

substring("$0", 1, 1) ought to return a $ sign, and if you use that as
an argument to replace(0 you'll get an error, because replace() wants
dollar signs to be followed by digits.

Hope that helps.

Liam

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Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
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