This is a classic case of premature evaluation. In the plot3d statement, the expression Shape(x,y) is evaluated as is, that is, with the symbolic constants x and y as arguments to Shape. Because their values are themselves, Maple cannot evaluate the conditional. There are a few ways to handle this. The simplest might be to just pass the procedure Shape to plot3d: plot3d(Shape, -100..100, -100); Note that the x and y ranges are passed as ranges, not as equations. Another possibility is to modify Shape to return an unevaluated function call to Shape when x and y are not numeric: Shape := proc(x,y) if x::numeric and y::numeric then `if`(x^2 + y^2 < (Diameter/2)^2, 1, 0); else 'Shape'(args); end if; end proc: A somewhat more robust approach would also check whether Diameter is numeric.

I'm unclear on what you are asking. Do you want the unevaluated function call myproc(x,y) to display as `x whatever y'? You can more or less accomplish that by creating a `print/myproc` procedure and using a neutral operator (see ?print and ?neutral for details).

`print/myproc` := proc(a,b) a &whatever b end proc:
myproc(a,b);
                  a &whatever b

Try using combine/power: y := 12/b/(b^s)*s/sin(Pi*b)^2*Pi^2; combine(y, power); 12/b^(s+1)*s/sin(Pi*b)^2*Pi^2

In html input mode, use &lt; and &gt; to input < and >, respectively. For an ampersand, use &

Just add the independent variables as arguments to a function call: y1(u1,u2), y2(u1,u2). A slightly nicer way to do this is to use the alias command (see ?alias for details): alias(y1=y1(u1,u2), y2=y2(u1,u2) ): J := (y1-y10)^2+(y2-Y20)^2+k*(u1)^2+k*(u2)^2: diff(J,u1); 2*(y1-y10)*(diff(y1, u1))+2*(y2-Y20)*(diff(y2, u1))+2*k*u1

Use the frontend command; it freezes various subexpressions.

z := a*f(x)+b*g(y)+c*x+d*y:
frontend(diff, [z,f(x)]);
                     a
frontend(diff, [z, x]);
                     c

The arguments of an unevaluated function call, which is what your exp(I*theta) is, can be extracted, as an expression sequence, using the op command:

op(exp(I*theta));
            exp*theta

Use op with an integer to extract a particular argument:

op(2, f(a,b,c));
                 b

Be aware that the Maple structure array has been largely superceded by Array. A simple procedure that does generates an Array, indexed from 0 to n and initialized with corresponding values 0 to n, is

MyArray := proc(n::nonnegint) Array(0..n, [seq(0..n)] ) end proc:

If you want to start the indexing from 1, you might use a Vector, which is, more or less, a one-dimensional Array with an index that starts from unity:

MyVector := proc(n::nonnegint) Vector([seq(0..n)]) end proc:

The problem is with the formal parameters. Indexed variables (the subscripted variables) don't work as formal parameters. Nor does the imaginary unit (by default `I'). It is, by the way, an appropriate place to ask.

For a few ideas, possibly not relevant to your application, you might look at a package I created quite a while ago, called manifold. It's written for Maple V R4, so is quite dated and rather crude. However, the documentation isn't too bad (there is a postscript of the typeset source code). It isn't limited to three dimensions and can integrate forms over manifolds. I don't have a local copy, but it is available here.

To generate all permutations, do

> with(combinat):
> perms := permute([1$9,2$9,3$9],9): # you don't want to print them
> perms[1];
         [1, 1, 1, 1, 1, 1, 1, 1, 1]
> perms[234];
         [1, 1, 1, 1, 3, 3, 2, 3, 3]
> perms[-1]; # last one
         [3, 3, 3, 3, 3, 3, 3, 3, 3]

To just count the number of permutations, you can do

> numbperm([1$9,2$9,3$9],9);
                19683

How long did you wait? Does your loop do anything? On my machine:

convert(90*time(proc() to 10^7 do od end())*Unit(sec), units, Unit(minute));
           4.528500000*Unit(min)

Maple V R5 is old; I don't have a version that runs on Linux, so can only give some hints. First, read the file as one long text string. One way is to read each line and catenate:

fd := fopen(filename);
input := "";
line := readline(fd);
while line <> 0 do
   input := cat(input,line);
   line := readline(fd);
od;
fclose(filename);

Now you need to convert `input' to a set of sets of characters. In Maple 10 this can be readily accomplished with

use StringTools in
  RegSplit("[^a-zA-Z]", input);
  map(str -> {op}(Explode(str)),{%});
  remove(`=`,%,{});
  map(curry(map,parse),%);
end use;

With Maple V you have some work to do. You'll need to use the substring command to access each character, then determine whether to convert it to a name (via parse) or to split the string and start a new set. I don't recall whether Maple V has any regular expression matching, I think not. So you might designate just a few characters as `splitters' (comma, space, newline) and check for those individually.

I've always used rpn (first was my dad's HP-35) and struggle with algebraic entry. I've owned an HP-15 since they came on the market (early 80s). About six years ago there was a version of Maple that ran on a handheld device, a Casioppia, I believe. I got to use it for a few months. It proved useful when I was consulting and didn't have a laptop (still don't).

Use the print command. If a copyright is included in the options statetement, you will also need to set interface(verboseproc=2), otherwise, in the gui it is displayed as proc() ... end proc.

interface(verboseproc=2):
print(simplify);