- From: Chan Cathy (Nokia-CTO/Boston) <cathy.chan@nokia.com>
- Date: Wed, 14 May 2014 15:00:06 +0000
- To: "ext Kostiainen, Anssi" <anssi.kostiainen@intel.com>, "Hirsch Frederick (Nokia-CTO/Boston)" <frederick.hirsch@nokia.com>
- CC: "public-device-apis@w3.org" <public-device-apis@w3.org>
Thanks Frederick and Anssi for the explanations. It makes better sense now. Still one question though: should a web app or UA trip on a negative finite value? The reason I ask is there's now a test case with a negative finite value. I wonder if that does more harm than good. In other words, are we incorrectly setting the expectation that negative finite values are a possibility? - Cathy. > -----Original Message----- > From: ext Kostiainen, Anssi [mailto:anssi.kostiainen@intel.com] > Sent: Wednesday, May 14, 2014 3:07 AM > To: Chan Cathy (Nokia-CTO/Boston); Hirsch Frederick (Nokia-CTO/Boston) > Cc: public-device-apis@w3.org > Subject: Re: [proximity] Meaning of negative values > > On 13 May 2014, at 17:11, Hirsch Frederick (Nokia-CTO/Boston) > <frederick.hirsch@nokia.com> wrote: > > > My understanding is that meaningful values are positive in the range of min > - max but that a 'negative infinity' value is used to represent 'undefined'. > > > > Value is a double so it can be negative, but only positive values have > meaning for this API. The negative infinity value is used as a special case > indicator to mean no value has been assigned (e.g. not supported or > available). > > Correct. > > > Thus for min, max and value the negative and positive infinity values are > used to indicate 'no defined value' - I guess Javascript NaN or 'undefined' > could be used instead of this convention, but this way it is always a number > and just requires a value test. > > This allows to differentiate between the "value is zero" and "value is not > known", and is easier to use with comparison operators than NaN or > undefined as Frederick notes. > > > I wonder if there is a documented set of conventions for the HTML5 family > of specs that would include this. > > The HTML spec does use this convention to set certain "not known" values as > negative or positive Infinity. The spec itself serves as a documented set of > conventions, and there's no separate maintained document for that, AFAIK. > > > The language about returning the 'value it was initialized to' is not very > clear. What it really means is 'return the value determined by the device > which is either the actual value or the indicator that no value is available'. > > The "value it was initialised to" is established language for initialising > attributes of an event, used by specification that make use of events. > > > Thus in general no negative values should be found other than negative > infinity. > > Correct. > > > Does this make sense? > > Thanks, > > -Anssi
Received on Wednesday, 14 May 2014 15:00:38 UTC