mailing-list for TeXmacs Users

[Karl Hegbloom <address@hidden>]

On Sat, 2007-06-02 at 15:43 +0100, Jeremy Henty wrote:
> On Sat, Jun 02, 2007 at 07:50:24AM +0200, Norbert Nemec wrote:
> 
> > If you don't like the space, try "<space> <tab>" which produces a
> > zero-width separator. This is useful, e.g. for multiple indices.
> 
> Aha, thanks!  The reason I was so grumpy earlier about inserting
> zero-width spaces was that I was going through the menus, I didn't
> know about the shortcut.  This is much better.

Sure, but to software that is reading the markup you've typed, perhaps
so that it can hand it on to a CAS or so that some nifty new TeXmacs
extension (probably yet to be written) can do some simple algebraic
operations on it, how is "w<space><tab>h" to be parsed?  What does it
mean?

"w*h" is obvious, and perhaps so would be "\var<enter>wh<right>" or
simply "wh", as a two character variable.  Perhaps "\var{wh}" would
display as math italic?  But when I look at that, how do I know whether
it's supposed to be seen as "w*h" or as "\var{wh}"?  It needs to be both
visually distinct to the human reader and easy to parse unambiguously
for the computer.  That's the future; it's where we're headed.  We want
to make CAS more natural to use, so you don't need the pencil and paper
anymore.  (Nobody's going to pay you $50 an hour to integrate by hand
when there's a CAS sitting by, right?)

Since you can think of a variable as something like a zero argument
function that returns the variable's current value, it makes sense to
typeset it in the same typeface as functions like "sin()".  It also
makes sense, from a data-entry standpoint, that it not require typing a
special macro to make a multi-letter variable a "variable".  It's name
alone signifies it's meaning uniquely enough, both to the human reader
and to the CAS parser.

One letter variable names are from the time when math was done with
pencil and paper, since it's less error prone and easier to transcribe a
single letter from one step to the next.  It takes less space on the
page too, so that's easier to read.  When you need the same letter
twice, you switch to Greek.

If you need a multi-letter variable name, it must be something special
relative to a regular old single-letter one, right?  And if it's
something different from that "function that returns the current value
of the variable", like maybe the value is of some special data type,
or... so then you would probably want to wrap it in a macro to get both
special typeset appearance AND distinct semantics for the CAS parser.

"d*x" is not the same thing as "differential(x)", right?  They are
conceptually similar in that the latter is sort of like multiplying "x"
by a very small number.  But "d*x" might be "distance times x", and if I
see a math italic "d", that's what I might parse it as.  It's easy to
press <tab> a few times after typing the "d", and your readers will pick
up on it quickly.

... except that I've never seen that on any of the stone tablets at the
old library.