[uebc2] Re: Items and indices
- From: Janet Reynolds <JReynolds@xxxxxxxxxxxx>
- To: "'uebc2@xxxxxxxxxxxxx'" <uebc2@xxxxxxxxxxxxx>
- Date: Fri, 25 Jul 2003 17:42:59 +1200
I'm sending this on behalf of Maria Stevens who is our new uebc2
representative. She is away for two weeks but we had already discussed Joe's
message and come to much the same conclusions as Stephen.
We preferred Option D which allows matching print grouping signs to define
an item. We did not think this made the definition more complex. Having
both print and braille grouping symbols round the same expression feels very
cluttered and not at all intuitive so it would be harder to write a rule
explaining why that has to happen. We did have a close look at Option B and
could see that this was workable but it is rather a fundamental change to
introduce at this stage and does increase the length of common expressions
like x squared and x sub 1 as Stephen pointed out. As far as negative
numbers in the superscript position are concerned, it is unfortunate that
they need braille grouping symbols but because of the need for plus and
minus signs to stand alone in Chemistry expressions I guess we've got to
live with that.
Maria and Janet, NZ
-----Original Message-----
From: Stephen.Phippen@xxxxxxxxxxx [mailto:Stephen.Phippen@xxxxxxxxxxx]
Sent: Tuesday, 22 July 2003 2:08 a.m.
To: uebc2@xxxxxxxxxxxxx
Subject: [uebc2] Re: Items and indices
From: Stephen Phippen
To: UEBC Committee 2
Date: 21 July 2003
Subject: Items and indices
Following Joe's message of 8 July, where he outlined the issues and
some options, I think I would reaffirm most of my view expressed in
my message of 6 June, i.e. that we should allow actual brackets to
imply braille grouping (or equivalently to extend the mechanism for
grouping to actual brackets). This is more or less Joe's option D,
but at the moment, I think I would restrict this to balanced brackets
only, for simplicity in reading; in cases where brackets are not
balanced, this would mean braille grouping brackets would be needed
to enclose the expression.
Following this route I can't see that the current rules would need
much other adjustment; and I think this rule will be natural,
and hence as easy, or easier for readers to remember than the
current UEBC rule where only the special braille brackets imply
grouping. (We might technically need a rule saying that when
a bracket in a relevant position is ONLY a single object and
not a grouping sign it should be enclosed in braille grouping
brackets, so the reader or translation software is not forever
looking for the matching bracket. However, this in reality
rarely happens, e.g. I don't think I've ever seen a superscript
consisting of an opening bracket only, though thinking of
the other applications of "items", you used to get a superposition
of right and left round brackets in algebra.)
Again, for simplicity of concept, I now think I would not extend the
group concept to cases such as numbers preceded by minus signs,
e.g. x superscript -2 would require the grouping signs around the
-2. This is a bit of an inconvenience, but there are common counter-
examples (e.g. superscript + and - signs in chemistry and particle
physics), where not regarding minus followed by a number as a group
is preferable. And the reader will have the clear concept that all
sequences of symbols in a superscript or subscript have to be grouped.
Thinking again about my superposition of round brackets case,
a variation of the above proposal that brackets imply grouping would
be to restrict it to superscripts and subscripts only. Looking at
the list of other cases, e.g. superposition, line through, etc.,
the concept doesn't seem very natural or useful apart from
superscripts and subcripts. (I suppose the reason why it is particularly
natural for superscripts and subscripts is that you might use
real brackets in just that way if you were writing the expression
linearly in print, e.g. 2^(x+y).) But if we had, say, AB with a bar over,
all enclosed on round brackets, we might allow the above general proposal
to let us write in braille (AB) bar over (even though the bar
did not strictly extend over the brackets), rather than ( open braille
grouping sign, AB, close braille grouping sign, bar over ). If
we did allow this, it would be a reason to retain the general form
of the proposal. If we didn't allow this (and I would probably
say we shouldn't in the spirit of UEBC), the general form of the
proposal would be fairly redundant outside superscripts and
subscripts, and very rarely a nuisance (as in my superposed
brackets case). The principle is that brackets imply grouping,
and the print bracket symbols are included in the grouping (as in
superscripts and subscripts).
On balance, I think I would therefore prefer to restrict brackets
implying grouping to superscripts and subscripts, though if the
above reasoning is correct, adopting the general form of the proposal
would in practice be harmless (if mostly useless!).
Joe's option B, to abandon the grouping concept for indices,
but to use an explicit terminator in all cases, initially
looked attractive to me, as it is similar to the BAUK method where we
use the ER sign to terminate indices. But in fact the cost of
the extra sign is very much offset in BAUK code by it not being
needed in many instances, in particular it is not used: after
simple superscript or subscript numbers, before spaces (which includes
before all arithmetical and most operator signs), before closing
brackets, at the end of mathematical expressions. These cover
the majority of cases, so the terminator is not used most of
the time.
This is not possible in UEBC - we would require the terminator
in all cases, which would amount to too much additional space used,
and, more importantly, to too much notational clutter. Think, for
example, of chemical formulae, as well as fairly basic maths
notation where x sub 1, x sub 2, etc. are frequently used as
variables.
-
NOTICE: The information contained in this email and any attachments is
confidential and may be legally privileged. If you are not the
intended recipient you are hereby notified that you must not use,
disclose, distribute, copy, print or rely on this email's content. If
you are not the intended recipient, please notify the sender
immediately and then delete the email and any attachments from your
system.
RNIB has made strenuous efforts to ensure that emails and any
attachments generated by its staff are free from viruses. However, it
cannot accept any responsibility for any viruses which are
transmitted. We therefore recommend you scan all attachments.
Please note that the statements and views expressed in this email
and any attachments are those of the author and do not necessarily
represent those of RNIB.
RNIB Registered Charity Number: 226227
Website: http://www.rnib.org.uk
* * *
* This message is via list uebc2 at freelists.org.
* To unsubscribe, send a blank message with
* unsubscribe
* as the subject to <uebc2-request@xxxxxxxxxxxxx>. You may also
* subscribe, unsubscribe, and set vacation mode and other subscription
* options by visiting //www.freelists.org. The list archive
* is also located there.
* The International Council on English Braille (ICEB) web site is
* http://www.iceb.org
* * *
* * *
* This message is via list uebc2 at freelists.org.
* To unsubscribe, send a blank message with
* unsubscribe
* as the subject to <uebc2-request@xxxxxxxxxxxxx>. You may also
* subscribe, unsubscribe, and set vacation mode and other subscription
* options by visiting //www.freelists.org. The list archive
* is also located there.
* The International Council on English Braille (ICEB) web site is
* http://www.iceb.org
* * *
Other related posts:
