It’s a rare week when I don’t discover some new corner of the language that I didn’t know about before. Did you know about per-variable typing?
let $a as xs:integer := 1
return $a + 2
=> 3
Sounds useless, doesn’t it? But just like function-parameter typing, it could prevent errors. Think about this:
let $a as element(ArticleTitle) :=
doc($ID)/MedlineCitation/Article/ArticleTitle
return $a
Now we have a guarantee that there will be exactly one ArticleTitle. Anything else will cause an error:
XDMP-AS: let $a as element(ArticleTitle) :=
doc($ID)/child::MedlineCitation/child::Article/child::ArticleTitle
return $a -- Invalid coercion: () as element(ArticleTitle)Nice, isn’t it?