This section contains a list of common Maple problems and their
solutions. You are also free to get help from your instructor or any
of the class helpers. The problems are listed in a rough order of
severity, from most to least. If you don't find your problem here, or
the suggestions don't work for you, ask for help!
- Maple just crashed
This happens from time to time. It may be caused by a bug in the
program, or by something you have done that has totally confused
Maple. The biggest danger is that you will lose your work. The best
defence is to save your worksheet often, using the Save
item on the File menu. Saving your work often can save you a
tremendous amount of time.
- Missing semicolon
Suppose you forget to put a semicolon at the end of a Maple command,
as in the following example. Notice that the syntax error appears
after the next command.
> p := x^2+3
> q := x^12;
syntax error:
q := x^12;
^
The fix is to go back to the first line and add the semicolon. This
usually does the trick. If it doesn't and you get another syntax
error, try issuing the first command again. If this doesn't solve the
problem, you might want to ask for help.
- Assigning and unassigning values to variables
Suppose you set a variable x to have the value 2, but later want
to use x as a variable again. The trick is to use the command x
:= 'x'; as shown below.
> x := 2;
> f := x -> x^2;
> f(x);
> diff(f(x),x);
Error, wrong number (or type) of parameters in function diff
> x := 'x';
> diff(f(x),x);
- Value not assigned
Suppose you forget the semicolon (:) in an assignment statement. Then
Maple will treat this as an equation and not an assignment. See the
following example.
> f := x -> x^2;
> a := 2;
> b = 2;
> f(a);
> f(b);
- Empty plot warnings
Sometimes Maple gives you the error message Warning in iris-plot:
empty plot and refuses to do the plot. The usual reason for
this error is that Maple can't compute numerical values of the expression
you asked it to plot. This can be caused by a your expression
depending on extra parameters or missing * for multiplication or
other syntax error in your expression. It can also happen if you try
to use
square brackets, [], or curly braces, {}, in expressions
to indicate association. You can only use parentheses, () for
this purpose. Maple use square brackets to indicate a list and curly
braces to indicate a set.
Some examples are shown below.
> q := x^2+xy-3;
> plot3d(q,x=0..1,y=0..1);
Warning in iris-plot: empty plot
> p := [sqrt(x)-1]^3;
> plot(p,x=0..1);
Warning in iris-plot: empty plot
- Problems with the seq command
The Maple seq command has the undesirable side-effect shown in
the example below.
> seq(i^2,i=1..5);
> i;
The side-effect is that the index variable i ends up having the value 6
after the seq command is executed. This is not a problem unless
you want to use i as a variable later on in your Maple session, as
shown in the example below. The last two commands in the example show
how to solve this problem.
> f := i -> i^3;
> f(i);
> i := 'i';
> f(i);
- Too many page breaks
This is a problem with a printed worksheet having too many page
breaks. The most likely cause is that your worksheet has double
separator lines. By default, a double separator line in a Maple
worksheet causes a page break at that point.
To fix this problem, open up your worksheet and delete any extra
separator lines. To delete a separator line, click on it with the
leftmost mouse button. (A very small black square will appear at the
left end of the separator line when you've selected the line
correctly. Make sure that this black square has appeared before going
on to the next step.) Select the Delete Cursor Region item from
the Edit menu, and the separator line should disappear. You can
also use the keyboard shortcut Ctrl+Del, i.e. pressing the
Ctrl key and the Delete key at the same time. Save
your worksheet to make the change effective before exiting Maple.
- Quota problems
Each user is allowed a certain amount, called a quota, of storage
space in their home directory. If you get a message saying you are
over quota when you log in, then you must delete some files. The
danger here is that you may not be able to save files until you are
back under quota.
Here are some things to watch out for.
- Keeping Maple plot files around after you've turned in the
lab. You should delete these files with the rm command after you
have printed them out.
- Pasting plots into your Maple worksheet. Avoid doing this. The
plots take up much more space when they are pasted into a worksheet
than they do saved as a separate file.
Suppose you had a file called junkfile in your home
directory. Then the command to delete this file is the following.
% rm junkfile
To remove all files of a certain kind, you can use the Unix wildcard
matching character *. For example, the command
rm *.ps
would remove all files ending with .ps from your directory.
