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


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 06:57:15 -0000

There is a mismatch in fold-right:

Signature:
   fn:fold-right( ., ., $f as function(item()*, item()) as item()*) as item()*

First parameter: item() sequence, second item()

Rules:
   else $f(fn:head($seq), fn:fold-right(fn:tail($seq), $zero, $f))

First parameter: item(), second item() sequence (the result type of $f)

-W

On 22/06/2014, Dimitre Novatchev dnovatchev@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Sat, Jun 21, 2014 at 11:08 PM, Wolfgang Laun
> wolfgang.laun@xxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
> wrote:
>>>
>>> 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 $f.
>>
>> -W
>
> About this remark: yes, and this means that there is a similar issue
> in the Error Conditions paragraph for fold-right.
>
> The signature of fold-right (as specified)  is:
>
>
>
> fn:fold-right($seq as item()*,
>                    $zero as item()*,
>                    $f as function(item()*, item()) as item()*) as item()*
>
> Do notice that the type of the argument $f is:
>
>        function(item()*, item()) as item()*
>
> The type of the 2nd argument is: item()  -- not a sequence.
>
> Therefore, if $f is passed as second argument a sequence ("$zero or
> the result of a previous application of $f") this would cause a
> dynamic error
>
>
>
> --
> Cheers,
> Dimitre Novatchev
> ---------------------------------------
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