re: MapAt complaint
- To: mathgroup at yoda.physics.unc.edu
- Subject: re: MapAt complaint
- From: wmm at chem.wayne.edu (Martin McClain)
- Date: Wed, 10 Nov 93 09:23:15 EST
Dear MathGroupers:
Here is an edited and improved exchange that gives me what I wanted
to know. Thanks to all who replied.
Regards- Martin
Part of my reply to Daniel Lichtblau, WRI:
Thanks, Daniel. My complaint is not so much about this particular example,
but rather it is the inability of MapAt to work on a selected set of parts
of an expression, treating them as a whole (particularly if they are just
some summands chosen out of a sum). Many Mma operators with part
specifications allow you to do this, but as far as I can see, MapAt does
not. For example:
In[1]: expr = 1+Sin[a+b]+Sin[a-b];
In[2]: Take[expr,{2,3}]
Out[2]: Sin[a+b]+Sin[a-b]
But if you try
In[3]:= MapAt[Simplify, expr, {2,3}]
ERROR: PART{2,3} DOES NOT EXIST
Often you can see some parts of a sum or a product that would simplify- it
makes you want to darken them with the mouse, and then apply some operator.
I asked Stephen Wolfram at the Mma Day in Ann Arbor whether the new mouse
facility in version 2.3 could select a part of an expression for this
purpose, and he showed me that it could. But can it select two or more
disparate parts and treat them as a whole? Alternatively, will MapAt will
be extended in version 2.3?
Thanks again- Martin
Daniel's reply:
I do not believe that MapAt will change in functionality,
but it may be that the "extraction" could happen under mouse control.
I'll ask around. If I learn anything I'll pass it on.
Later, via danl:
Begin forwarded message:
Date: Tue, 9 Nov 1993 16:43:31 -0800
From: Neil Soiffer <soiffer>
To: danl at wri.com
Subject: Re: MapAt complaint
Cc: wri-kernel at wri.com
In 2.3, you can select an arbitrary subexpression (such as "b+c" in
"a+b+c").
You can then do what you want with it. For the particular example,
clicking on the "Simplify[]" palette button will cause an inplace
simplfy to occur, with the result displayed on a new line below.
2.3 will not have the ability to make multiple selections.
That will come in 2.4 or later. You can, of course, do a copy and a
paste into a new cell, copy the next thing, paste, etc.
Neil