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Re: LeafCount Question

• To: mathgroup at smc.vnet.net
• Subject: [mg25802] Re: LeafCount Question
• From: "Hans Staugaard" <hans.staugaard at get2net.dk>
• Date: Sat, 28 Oct 2000 01:40:57 -0400 (EDT)
• References: <8t63s9$eg2@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hello

Here's a quick fix.

First a check to see that the ordering is 'wrong':

In[1]:=
2c - 2a - b + d

Out[1]=
-2 a - b + 2 c + d

Then my fix

In[2]:=
Unprotect[Plus];

In[3]:=
Format[Plus[negs : (Times[_?Negative, _] ..), poss__]] :=
  SequenceForm[Plus[poss], negs]

In[4]:=
Protect[Plus];

Now check that the ordering is 'right'

In[5]:=
2*c - 2a - b + d

Out[5]=
2 c + d-2 a-b

Note that there are problems with the operator spacing.

Hans

"Dana" <dana_news at hotmail.com> wrote in message
news:8t63s9$eg2 at smc.vnet.net...
> Hello.  Using Mathematica 4.0  When one solves equations, I get a little
frustrated
> when the answers come out as
> -A +B, when the answer looks much better as...
> B - A
>
> I was hoping that the "LeafCount" would be smaller with my "preferred"
way,
> but for some reason, it does not look like there is a difference.
>
> In[19]:=
> {LeafCount[-B + D], LeafCount[D - B]}
>
> Out[19]=
> {5, 5}
>
>
> Here is a simple Solve, and it is a little embarrassing to say the answer
is
> (-B + D)..Etc when  everyone else will have to change this  manually to
(D -
> B)...ect.
>
> Is there a way around this?  Again, I was hoping LeafCount would do the
> trick, but it apparently does not.
> Thank you in advance.  Dana.
>
> FullSimplify[Solve[{Y == A*X + B, Y == C*X + D}, {X, Y}],
>   ComplexityFunction -> LeafCount]
>
> {{X -> (-B + D)/(A - C), Y -> (-(B*C) + A*D)/(A - C)}}
>
>
>
> Since I am new to Mathematica, I noticed the following...
> Internally, it looks like no difference.  It is just frustrating.
>
> In[25]:=
> {FullForm[(-B + D)], FullForm[(D - B)]}
>
> Out[25]=
> {Plus[Times[-1, B], D], Plus[Times[-1, B], D]}
>
>
>
>