Subject: Re: [xsl] The specification of the standard function fold-left From: "Wolfgang Laun wolfgang.laun@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Sun, 22 Jun 2014 06:08:46 -0000 |
A couple of remarks: On 22/06/2014, Dimitre Novatchev dnovatchev@xxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > The section "16.2.3 fn:fold-left" of the W3C document "XPath and > XQuery Functions and Operators 3.0", contains this text: > > "As a consequence of the function signature and the function calling > rules, a type error occurs if the supplied function $f cannot be > applied to two arguments, where the first argument is either the value > of $zero or the result of a previous application of $f, and the second > is $seq or any trailing subsequence of $seq" > > The signature of the function fold-left is specified as: > > fn:fold-left($seq as item()*, > $zero as item()*, > $f as function(item()*, item()) as item()*) as item()* > > The above quoted paragraph violates the signature, because the > argument $f, as specified cannot have as its second argument a > sequence -- the type of the second argument of $f must be item(). But > the above quoted paragraph says "...the second is $seq or any trailing > subsequence of $seq". Since each call of $f is done with fn:head($seq), and the restriction defined here refers to the second argument of fn:fold-left I see no problem with this text. > > Exactly the same paragraph is used in the specification of fold-right > -- and in that case the text is correct. The paragraphs headed "Error Conditions" do differ: ...either the value of $zero or the result of a previous application of $f, and the second is $seq or any trailing subsequence of $seq. ...any item in the sequence $seq, and the second is either the value of $zero or the result of a previous application of $f. -W > > It seems that the paragraph was copied from the fold-right > specification into the specification of fold-left and this led to the > observed error. > > Hope this would help and lead to a future correction. > > -- > Cheers, > Dimitre Novatchev > --------------------------------------- > Truly great madness cannot be achieved without significant intelligence. > --------------------------------------- > To invent, you need a good imagination and a pile of junk > ------------------------------------- > Never fight an inanimate object > ------------------------------------- > To avoid situations in which you might make mistakes may be the > biggest mistake of all > ------------------------------------ > Quality means doing it right when no one is looking. > ------------------------------------- > You've achieved success in your field when you don't know whether what > you're doing is work or play > ------------------------------------- > To achieve the impossible dream, try going to sleep. > ------------------------------------- > Facts do not cease to exist because they are ignored. > ------------------------------------- > Typing monkeys will write all Shakespeare's works in 200yrs.Will they > write all patents, too? :) > ------------------------------------- > I finally figured out the only reason to be alive is to enjoy it.
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