@vs140580  Remove the  print  command from the body of your procedures:

trying_new.mw

@vs140580  I don't understand why you can't do this:

op(0,RandomTools:-Generate(choose({A(Graphln, k),B(Graphln, k),C(Graphln, k)})));

@Carl Love  Thanks, I've edited my answer.

@nm  Thanks a lot for the answer!

@acer  Thanks a lot for the detailed answer!

@mmcdara  I agree, but this is not a fundamental difference. We can add the  collect  command:

x^(n-1)*(collect(expand((n*x^n - 2*n*x^(n - 1) + x^n)/x^(n-1)), x));

@lcz If you are interested in arbitrary set partitions, you can also take a look at my  post  https://mapleprimes.com/posts/200776-Partition-Of-A-Set-Into-Parts-Of-Any-Sizes .  It was written long ago, when Maple didn't have the  Iterator package yet.

@Deeshani 

 

Download metriccalculaions_new_(12).mw

@dharr  OK. Vote up.

@ecterrab In fact, the exact solution is easily expressed explicitly (see below). But a natural question arises: why does this solution not continue to the right from  x~2.55 , as shown by the numerical solution?

restart;
ode:=diff(y(x),x,x)+2*diff(y(x),x)^2+8*y(x)=0:
ics:=y(0)=0, D(y)(0)=1:
dsolve({ode, ics}, y(x), implicit);
value(%);
isolate(%, y(x));
sol := simplify(%);
odetest(sol, [ode, ics]);

@Thomas Dean  Using the P procedure, you can plot the body of revolution for any value of the parameter  a  (this is the angle of rotation).  P (2*Pi+Pi/2)  will be the whole body:

P(5*Pi/2);

@Axel Vogt  A good idea! This can be done even without using the plottools package:

restart;
plot([erf(y),y, y=-3..3]);

@Christian Wolinski 

It takes approximately 10 sec in Maple 2018.2.

@zenterix  In 2d input use prefix (Polish) notation:

A:=<1,2;3,4>: B:=<6,7;8,9>:
`%.`(A,B)=A.B;

@acer  Thank you! I tried the  convert(..., factorial)  command, but for some reason did not think to apply the  expand  one. In Maple 2018, your method also works.