MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

RE: RE: Why do parentheses spuriously appear when I type in a formula?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34547] RE: [mg34458] RE: [mg34410] Why do parentheses spuriously appear when I type in a formula?
  • From: "DrBob" <majort at cox-internet.com>
  • Date: Mon, 27 May 2002 01:16:44 -0400 (EDT)
  • Reply-to: <drbob at bigfoot.com>
  • Sender: owner-wri-mathgroup at wolfram.com

I agree you should be able (somehow) to control this behavior to your
satisfaction.  However... depending on the audience you're writing for
(remember them?)... it is risky to deviate from "convention".

It makes sense to me for subscript to have higher precedence (bind
tighter, if you will) than superscript --- just as Times has higher
precedence than Plus.  It will make sense to many people, and I suspect
that's why it's done that way in Mathematica.  The precedence has to go
SOME direction, so you choose one, and in this case it's chosen
(unfortunately perhaps) partly because of the confusion of Power with
Superscript.

Sometimes we want a Superscript NOT to mean Power, and it's difficult to
do that.  THAT can be really annoying.

Bobby

-----Original Message-----
From: Wolf, Hartmut [mailto:Hartmut.Wolf at t-systems.com] 
To: mathgroup at smc.vnet.net
Subject: [mg34547] RE: [mg34458] RE: [mg34410] Why do parentheses spuriously
appear when I type in a formula?


> -----Original Message-----
> From: DrBob [mailto:majort at cox-internet.com]
To: mathgroup at smc.vnet.net
> Sent: Thursday, May 23, 2002 7:27 PM
> Subject: [mg34547] RE: [mg34458] RE: [mg34410] Why do parentheses spuriously
> appear when I type in a formula?
> 
> 
> >>the b subscript of T raised to the a power
> 
> I read that wrong before.  Sorry.
> 
> If you mean (the b subscript of T) raised to the a power, the 
> keystrokes
> are T Ctrl-_ b Ctrl-space Ctrl-^ a, and there are no parentheses.

[Hartmut Wolf]
Why not? I could argue: who tells subscript it must be effective before
supercript applies? The convention is our reading convention
left-to-right
subscript comes before suberscript, such it comes first.

> 
> If you mean the b subscript of (T raised to the a power), the 
> keystrokes
> are T Ctrl-^ a Ctrl-space Ctrl-_ b, and there MUST be parentheses in
> order to distinguish between that and the other answer.  If you care.
> If you don't, then use the other method and avoid the parentheses.
> 
[Hartmut Wolf]
Same argument as above, but now uttered: why? This has nothing to do
with
care or not, just with easy reading.

Don't forget: the interpretation of Superscript as Power comes later at
expression formation, and not at box building. But it is there where the
parentheses are introduced. There are not wrong, but nasty, esp. if you
want
to define a tensor with mupltiple co- and contravariant indices (no
power in
sight) as Carl Woll tried (if I'm right). See

    a  d    g
(((T )  )    )
      b  e f  h

the parentheses are absolutely redundant!

I normally don't complaint if my tool doesn't meet my first expectations
(or
doesn't supply the universal "solve"-button), instead I search for a way
to
get the best out of it. What disturbs me (and I think Carl too) more is
that
I found no way to change this behaviour: the first point to intervene is
at
MakeExpression (which corresponds to the semantic actions of a parser),
but
everything happend before.

> I see no other reasonable way to read it, and I see no reliable way to
> visually distinguish between the two forms without 
> parentheses in one of
> them.
> 
> >>You can also check the input which does work: first the subscript,
> then the subscript; the ctrl-space escape *is* needed!
> 
> That's obviously a typo... so I still haven't seen the answer you DO
> want.
> 
> Bobby
> 
---snipped---

the cases of input which might read as ambiguous 

In[25]:= \(T\^a\%b\)
Out[25]= SubsuperscriptBox[T,b,a]

In[27]:= \(T\_b\%a\)
Out[27]= SubsuperscriptBox[T,b,a]

aren't because the are mapped to the same internal (and visual)
representation

--
Hartmut





  • Prev by Date: RE: RE: plotting with boundary conditions
  • Next by Date: RE: : Re: Help! How to calculate additive partitions?
  • Previous by thread: RE: RE: Why do parentheses spuriously appear when I type in a formula?
  • Next by thread: Re: Why do parentheses spuriously appear when I type in a formula?