If f is a procedure e.g.  f := x -> x^2;  then f[a](b)  evaluates to f(b)  (= b^2).
Do you know where is this feature documented?
(I have used this in the past, but I need now a reference and I cannot find it).

1/0;
Error, numeric exception: division by zero
lastexception;
            0, "numeric exception: division by zero"
lastexception; # ???
            Typesetting:-Typeset, "invalid input: %1 expects %2 arguments, but received %3", type, 2, 3

So, printing lastexception produces a new error!
When typesetting=standard, it's OK.

L:=[1,2,0,4]:
s := sum(1/L[i], i=1..nops(L));

Error, (in limit/mrv/limsimpl) too many levels of recursion

So, this error cannot be caught by try

try    # bug
  s := sum(1/L[i], i=1..nops(L));
  catch:  s:=infinity
end try;

Error, (in limit/mrv/limsimpl) too many levels of recursion

Strangely, for L:=[1, 2, 0.0, 4]  it's OK.

Everything works with add instead of sum, but this is another thing.

seq(x) in the help page:  When x is a sparse Matrix, Vector or rtable, only the nonzero entries are scanned.
Is the statement correct/complete?

V := Vector(6, [11,22,0,44], storage=sparse):
entries(V);
seq(V);

                        [11], [22], [44]
                      11, 22, 44, 0, 0, 0