MuPAD-FAQ-HOWTO

## How to ... in MuPAD ?

Also refer to Problems with ... in MuPAD ? which offers hints and work arounds for well known problems.

1. ... insert comments ?
2. ... read-in a file of commands ?
3. ... unassign a variable ?
4. ... define a matrix ?

1. ... insert comments ?
   In MuPAD programs comments are enclosed between two hash symbols # and #.

       >> pi:= float(PI);  # it's a comment #  e:=float(E);

2. ... read-in a file of commands ?
   During a MuPAD session the function read can be used to read command files.

       >> read( "file" );

   On UNIX systems also the pipe mechanism of the shell can be used to start MuPAD with a special command file. This is often used for batch processing and also for demos.

       # cat in.mu
       fact(20); # this is factorial of 20 #
       quit;

       # mupad < in.mu
       >> fact(20); # this is factorial of 20 #
       2432902008176640000

       &> quit;
       #

3. ... unassign a variable ?
   Variables can be unassigned (returned it to its symbolic status) by assigning the value NIL.

       >> x:=42; x:= NIL: x;
       42
       x

4. ... define a matrix ?
   First load the linalg package, then define a matrix constructor with Matrix(D) or SquareMatrix(n,D) where D is a domain (the default is ExpressionField()) and n is an integer.

       >> loadlib("linalg"):
       >> M := Matrix(Rational):
       >> A := M([[1/2,1/3,3/5],[5/7,3,9/2]]);

                                   +-               -+
                                   | 1/2 , 1/3 , 3/5 |
                                   |                 |
                                   | 5/7 ,  3  , 9/2 |
                                   +-               -+

       >> N := SquareMatrix(2):
       >> B := N([[cos(x),sin(x)],[exp(x),ln(x)]]);

                                   +-               -+
                                   | cos(x) , sin(x) |
                                   |                 |
                                   | exp(x) , ln(x)  |
                                   +-               -+