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Re: [xsl] The specification of the standard function fold-left

2014-06-22 01:21:10
On Sat, Jun 21, 2014 at 11:08 PM, Wolfgang Laun
wolfgang(_dot_)laun(_at_)gmail(_dot_)com 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>
wrote:
"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.

The issue is that by definition the second argument of $f is of type
item()  -- this means that $f cannot accept as its second argument
"$seq or any trailing
subsequence of $seq".

And you are referring to the XQuery and XSLT code published in the
"Rules" section -- this code is correct. The issue is with the text of
the "Error Conditions" section -- more precisely, the end of the
sentence.



-- 
Cheers,
Dimitre Novatchev
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Truly great madness cannot be achieved without significant intelligence.
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Never fight an inanimate object
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To avoid situations in which you might make mistakes may be the
biggest mistake of all
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Quality means doing it right when no one is looking.
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You've achieved success in your field when you don't know whether what
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I finally figured out the only reason to be alive is to enjoy it.
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