It is a recurrent theme, but I think that a wiki could help a lot with deficiencies of documentation in some areas like this one.

It is a recurrent theme, but I think that a wiki could help a lot with deficiencies of documentation in some areas like this one.

for those examples. And only one example for 'evalapply' itself...

for those examples. And only one example for 'evalapply' itself...

I find that this latter issue on functional style programming is barely mentioned in the documentation. In ?examples,functionaloperators :

Operators are transitive.

(a+b)(t);

	a(t)+b(t)
...

and may be not much more elsewhere.

By the way, I would call this property as distributive.

I find that this latter issue on functional style programming is barely mentioned in the documentation. In ?examples,functionaloperators :

Operators are transitive.

(a+b)(t);

	a(t)+b(t)
...

and may be not much more elsewhere.

By the way, I would call this property as distributive.

Note that the author uses the 'linalg' package that is obsolete. You should better look at the package 'LinearAlgebra'.

Note that the author uses the 'linalg' package that is obsolete. You should better look at the package 'LinearAlgebra'.

DepVars := [Q(theta, `ϕ`),S(theta, `ϕ`)];
BJ:= PDEtools:-ToJet(B, DepVars);
select(has,BJ,Q):
DQ:=subs(Q=D,D[]=1,%);
select(has,BJ,S):
DS:=subs(S=D,D[]=1,%);
DS*S+DQ*Q;

(D[2, 2]+cos(theta)*sin(theta)*D[1]-4*sin(theta)^2*M*G*k
-4*sin(theta)^2*M*G*k*D[1, 1]-sin(theta)^2*D[1, 1])*S
+(D[2, 2]+cos(theta)*sin(theta)*D[1]+4*sin(theta)^2*M*G*k*D[1, 1]
+4*sin(theta)^2*M*G*k-sin(theta)^2*D[1, 1])*Q; 

DepVars := [Q(theta, `ϕ`),S(theta, `ϕ`)];
BJ:= PDEtools:-ToJet(B, DepVars);
select(has,BJ,Q):
DQ:=subs(Q=D,D[]=1,%);
select(has,BJ,S):
DS:=subs(S=D,D[]=1,%);
DS*S+DQ*Q;

(D[2, 2]+cos(theta)*sin(theta)*D[1]-4*sin(theta)^2*M*G*k
-4*sin(theta)^2*M*G*k*D[1, 1]-sin(theta)^2*D[1, 1])*S
+(D[2, 2]+cos(theta)*sin(theta)*D[1]+4*sin(theta)^2*M*G*k*D[1, 1]
+4*sin(theta)^2*M*G*k-sin(theta)^2*D[1, 1])*Q; 

that you may use just for display purposes:

diff(Q(theta, `ϕ`), `ϕ`, `ϕ`)
+diff(S(theta, `ϕ`), `ϕ`, `ϕ`)
+(diff(S(theta, `ϕ`), theta)+diff(Q(theta, `ϕ`), theta))
*cos(theta)*sin(theta)+(4*M*G*k*(diff(Q(theta, `ϕ`), theta, theta))
-4*M*G*k*S(theta, `ϕ`)+4*M*G*k*Q(theta, `ϕ`)
-4*M*G*k*(diff(S(theta, `ϕ`), theta, theta))
-(diff(S(theta, `ϕ`), theta, theta))
-(diff(Q(theta, `ϕ`), theta, theta)))*sin(theta)^2;
B:=expand(%);
BQ:=select(has,B,Q):
BS:=select(has,B,S):
subs(Q=`Q `,BQ)+subs(S=`S `,BS);

that you may use just for display purposes:

diff(Q(theta, `ϕ`), `ϕ`, `ϕ`)
+diff(S(theta, `ϕ`), `ϕ`, `ϕ`)
+(diff(S(theta, `ϕ`), theta)+diff(Q(theta, `ϕ`), theta))
*cos(theta)*sin(theta)+(4*M*G*k*(diff(Q(theta, `ϕ`), theta, theta))
-4*M*G*k*S(theta, `ϕ`)+4*M*G*k*Q(theta, `ϕ`)
-4*M*G*k*(diff(S(theta, `ϕ`), theta, theta))
-(diff(S(theta, `ϕ`), theta, theta))
-(diff(Q(theta, `ϕ`), theta, theta)))*sin(theta)^2;
B:=expand(%);
BQ:=select(has,B,Q):
BS:=select(has,B,S):
subs(Q=`Q `,BQ)+subs(S=`S `,BS);

So, may be if George Labahn is reading this thread, he may post a pointer to a review/introduction to this subject. If possible, written for non-mathematicians, with applications in mind, and showing how to use Maple command options to get good approximations.

So, may be if George Labahn is reading this thread, he may post a pointer to a review/introduction to this subject. If possible, written for non-mathematicians, with applications in mind, and showing how to use Maple command options to get good approximations.

Ie there are things that are "remembered" across the execution of 'restart'. Eg. execute in a fresh (Windows) session:

currentdir("c:/");
restart:
currentdir();