Re: proposal to toss out text2interval. Was: dependent and independent intervals, proposal to toss out text2interval.
Folks,
Am Tue, 19 Feb 2013 12:37:40 -0800
schrieb Richard Fateman <fateman@xxxxxxxxxxxxxxxxx>:
> On 2/19/2013 2:00 AM, Guillaume Melquiond wrote:
> .... snip, , expressions meaning what they say...
>
> I think that whatever advantage can be gained by allowing an
> implementation to process string expressions like "0.1 + pi" is more
[...]
probably I'm missing something here. But where does the idea to allow
"0.1 + pi" as an input to text2interval come from?
The current draft contains references to text2interval
1) in the Level 1 part
Here any understandable argument to text2interval is allowed,
including things like "0.1 + pi"
2) in the Level 2 part
There are a handful of references here, all of them finally
leading to 11.11.8 Constructors, which reads:
> "text2interval.
> Input s to the constructor text2interval(s) is a text string. The
> constructor call succeeds if the implementation determines that s is a
> valid interval literal with value x, see §11.11.1 [...]
> Otherwise the call fails and the result is Empty."
Thus text2interval requires a valid literal on this level. A valid
literal is in turn defined in 11.11.1, which essentially defines a
syntax for [inf,sup] and <mid+-rad> with strings for empty, entire and
infinity.
There is also the mention of an language- or implementation-defined
enhanced syntax which may includes other symbols for real constants
like Pi in floating literals, but---besides this being language- or
implementation-defined---nothing is expressions.
Nowhere is there any mention of more complex expressions as a valid
interval literal. Where is this discussion coming from?
Best regards,
Christian