Re: dependent and independent intervals, proposal to toss out text2interval. Was re: about emp (was: Motion 42:no)
Richard
On 3 Mar 2013, at 15:54, Richard Fateman wrote:
> One could write it then, in pseudo-code as
>
> text2interval(s):=
> look for [A,B]; return (nums2int( read_from_string(A), read_from_string(B))
> look for <A+-B> ; return mid-rad version
> look for [A], do whatever is decided.
>
> This same data could be generated by separating the strings for A and B and
> writing a short program...
>
> lo:=read_from_string (A);
> hi:= read_from_string(B);
> nums2int(lo,hi)
>
> thereby eliminating text2interval.
> Actually it would be eliminating IEEE754double_text2interval, IEEE754single_text2interval ...
Well no, because this algorithm doesn't take into account the destination interval type T, which at Level 2 must be pre-specified. Let T be an inf-sup type, as you always seem to assume that. Then lo needs to be rounded down and hi rounded up.
> On the other hand I object to (b) if it eliminates or deprecates in some way the
> option of creating intervals with rational endpoints as text2interval("[1/10,1/3]")
You need to look at the Vienna proposal. No one in the group up to now has argued strongly that 1788 *must* support exact rational interval literals, which is what you seem to say here. Though I think Alan Eliasen and Dima Nadezhin may be on your side.
John