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Re: ACTION-2029 - Check that integer promotes successfully to double

From: Nick Van den Bleeken <Nick.Van.den.Bleeken@inventivegroup.com>
Date: Fri, 11 Sep 2015 13:15:27 +0000
To: Erik Bruchez <erik@bruchez.org>, Forms WG <public-forms@w3.org>, "public-xformsusers@w3.org" <public-xformsusers@w3.org>
Message-ID: <7A7E64D4-B327-40A2-9A92-E90DEC02610A@inventivegroup.com>

Isn’t for the input parameter value of NaN returning an empty sequence not quite close to an empty string? When the sequence is converted to a string it will be an empty string. And in a lot of cases we convert to string in XForms. There are of course cases where there will be a difference. But I think that the advantages of returning an xs:date (or xs:dateTime) overweigh the impact of the backwards incompatibility.


Nick Van den Bleeken

From: <ebruchez@gmail.com<mailto:ebruchez@gmail.com>> on behalf of Erik Bruchez
Date: Wednesday 2 September 2015 06:49
To: Public Forms, "public-xformsusers@w3.org<mailto:public-xformsusers@w3.org>"
Subject: ACTION-2029 - Check that integer promotes successfully to double
Resent-From: <public-xformsusers@w3.org<mailto:public-xformsusers@w3.org>>
Resent-Date: Wednesday 2 September 2015 06:50


This is the case AFAICT, for example, in XPath 2.0:

        $sourceString as xs:string?,
        $startingLoc as xs:double
    ) as xs:string

        $sourceString as xs:string?,
        $startingLoc as xs:double,
        $length as xs:double
    ) as xs:string

I assume that, for compatibility with XPath 1.0, these functions take `xs:double` parameters. I checked that, with Saxon at least, passing an `xs:integer` works, as we had suspected was the case based on the spec, namely:

- you can pass an `xs:decimal` to an `xs:double`, possibly with loss of precision
- `xs:integer` is a subtype of `xs:decimal`
- therefore you can pass an `xs:integer` to an `xs:double`

This means that the following XForms functions can take `xs:double`:

- `days-to-date()` [1]
- `seconds-to-dateTime()` [2]

and so I fixed the types in the spec:


Doing so, I have found another issue in these two functions, namely the following language from XForms 1.1:

> An input parameter value of NaN results in output of the empty string.

With the change to `xs:double`, the function parameters are now backward-compatible. But the return types are not: in XForms 1.1, they were `string`, and here they are `xs:date` or `xs:dateTime`.

We can either:

1. Change back the return types to `xs:string`, which is compatible with XForms 1.1, but not XPath 2.0-friendly,
2. or use `xs:date?` and `xs:dateTime?` return types. A `NaN` parameter returns the empty sequence.


[1] https://www.w3.org/MarkUp/Forms/wiki/XPath_Expressions_Module#The_days-to-date.28.29_Function

[2] https://www.w3.org/MarkUp/Forms/wiki/XPath_Expressions_Module#The_seconds-to-dateTime.28.29_Function

Received on Friday, 11 September 2015 13:16:02 UTC

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