## 12785 Reputation

8 years, 321 days

## f[a](b) (indexed function) ...

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).

## lastexception and typesetting...

Maple

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.

## A bug in finite sum...

Maple
```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 for sparse rtables...

Maple

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

Maple
 (1)
 (2)
 > value(S);

It seems that the inner add is evaluated prematurely.