Re: Fwd: Pattern matching error in xsl:key

The source of the surprise is not that the select parameter is evaluated.
It's because the value in the attribute is type annotated as xs:string even
though it is a decimal number.

So you think you are comparing 4.0 to 4.0 but because of the type value
assigned to the RHS the comparison is actually 4.0 to '4.0'

Both Dmitre and Martin explained this earlier in the thread.



On Sun, Sep 6, 2020 at 4:22 PM Chapman Flack <chap-JULfBfA8satPFr4CO1/[email protected]> wrote:

> On 09/06/20 15:03, Ihe Onwuka wrote:
> >> Maybe you would find XML Query more to your liking?
> > ......what I posted earlier about offering patronising explanations.
>
> It was offered as a straight suggestion. There are two very closely related
> languages with very similar capabilities, and one of them is free of the
> property you don't like.
>
> I will freely admit that I too find XML Query more comfortable to read and
> to write, for some of the same reasons; I generally write XSLT only when
> some external constraint makes it necessary, or when it is clearly better
> suited to a particular task.
>
> When I do (have to) write XSLT, I do spend time double checking where
> things
> represent data and where they represent code. But I understand it was a
> deliberate design objective that XSLT be itself represented as XML, and
> the fact that the same lexical XML can be code in some cases and not in
> others is a consequence of that, and I just need to know which cases are
> which.
>
> If you say in JavaScript:
>
>   '4.0'.endsWith(eval('4.0'))
>
> the result is false. Both strings here have the same lexical form; the
> second one has to be understood as code, because it occurs inside eval().
> You know that because you know how eval() works, not because the string
> looks different. There, too, you can add quotes and
>
>   '4.0'.endsWith(eval('"4.0"'))
>
> will be true. In XSLT you know the select='4.0' in a <param> represents
> code, because you know how <param> works.
>
> Compared to JavaScript, XSLT gives you more choices how you could rearrange
> that to express most precisely what you mean. Among
>
> <param name='source' select='"4.0"'/>
> <param name='source' as='xs:string'>4.0</param>
> <param name='source' select='4.0 cast as xs:string'/>
>
> the first two give you the same result, with the second one arguably
> expressing the intent more clearly; the third would give a result you
> don't want in this case, but could be the clearest way to express
> intent in some other case where that was the wanted behavior.
>
> It seems to me that the object of the game in any language is, ok, if
> I am going to write this thing in language X for whatever reason, how
> do I use the features of language X to express the intent as clearly
> as I can?
>
> Getting back to the original intent you were trying to express, this
> thread has presented some workable and clear ways to express it.
>
> Regards,
> -Chap
>

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