Hi everyone, im new and this is my first question here.

I’m wondering why this is not possible:

If i Type:

```
A=[1.0, 2.0, 3.0, 4.0, 5.0];
B=zeros(5);
```

and then

```
sum(A)=B[1]
```

i get the error Message:

```
error in method definition: function Base.sum must be explicitly imported to be extended
```

Why is this ?

Typing

```
typeof(sum(A))
```

its Float64 like the elements of B?

also

```
sum(A[1:3])=B[1]
```

does not work , but now with the error mesasage:

```
syntax: "A[1:3]" is not a valid function argument name
```

Thanks