## Possible Bug in Maple ...

Hey,

I think I found a bug concerning the useage of assume and alias:

 > restart:
 > alias(a=a(t),b=b(t));
 (1)
 > assume(a(t),real);
 > getassumptions(a(t));
 (2)
 > assume(b(t),real);
 > getassumptions(a(t));
 (3)
 > getassumptions(b(t));
 (4)
 >
 >
 >

Commenting out the alias command produces correct results. I am on linux with build 922027.

alias_bug.mw

## About alias: How can one convert back to an expres...

Hi!

I use 'alias' to define variable dependencies.
But when I want to use the result of my calculation as an expression, I bite the dust; I cannot get rid of the dependencies.
Can anyone help me here?

In the simplified example below, I use the independent variables z[3] and z[4] to define z[1](z[3],z[4]) and z[2](z[3],z[4]).
I then introduce a function f[1](z[3],z[4]) and its derivatives df_dz.
I introduce the names dz[1]/dz[3]=Dp[1,3], dz[1]/dz[4]=Dp[1,4] etc...
When I have calculated df_dz[3], however, I cannot insert values of z[2] without affecting Dp[2,3].
Actually, now I have finished my calculation and want df_dz[2,3] to be a regular expression, so that I can insert values of
z without affecting the Dp:s.
How can I convert df_dz[3] to a regular expression?

alias( seq(z[i]=z[i](seq(z[j],j=3..4)),i=1..2)):
alias(f=f(seq(z[j],j=3..4))):
alias(seq(seq(Dp[m,n]=diff(z[m](seq(z[j],j=3..4)),z[n]),m=1..2),n=3..4)):

f:=z[1]-z[2]*z[3]:

for j from 3 to 4 do
df_dz[j]:=diff(f,z[j]);
od:

df_dz[3];
subs(z[2]=4711,df_dz[3]);
whattype(Dp[1,3]);
whattype(z[3]);

function

indexed

## How do I preform a particular substitution?...

I am trying to do a substitution as shown in the attached document. I know variants of this question have been asked before but dont quiet get what to do. It is problem with algsubs and how it handles denominators I think. Can get substiturion to work for simple fractions but more complicated ones fail. Would appreciate any guidance here.

 (1)

 (2)

 (3)

 (4)

 (5)

 (6)

 (7)

 (8)

 (9)

 (10)

 (11)

 (12)

## Why should one use alias vs. := ?...

One can write

restart;
alias(C=binomial);
C(4,2);

or

restart;
C:=binomial;
C(4,2);

and then both work the same. In the first case, the replacement of "C" by "binomial" is done at parsing time before evluator gets hold of the code, while in the second case, the replacement is done at run-time (evaluation).

So alias will be more efficient and more safe, I assume.

Is that all there is to it, or are there other more subtle and important reasons to use alias vs. :=  when one want to bind long name to smaller ones to save on typing.

## How can I simplify an equation?...

Hi guys, I am new on maple I have a simple question for you.

Let's say

Then let's say

Maple give me as result something like  instead of

And let's say  I get  instead of

My equation is more complicated than these but the problem is the same.

I hope I was clear in the explanation of the problem :)

Thanks :)

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