I just started learning Scala, so please be patient :-)

I have a question about how reduceLeft behaves. Here an example:

```
List(1, 2, 3, 4, 5) reduceLeft (_ + _)

```

I wonder if the calculation can be done simultanously, e.g.:

first round:

* process 1 calculates: 1 + 2
* process 2 calculates: 4 + 5

second round:

* process 1 calculates: 3 + 3

third round:

* process 1 calculates: 6 + 9

At least that's what I would expect to happen if I just use the reduce function instead of reduceLeft. Or does reduceLeft really only does one reduction at a time?

```
((((1 + 2) + 3) + 4) + 5)

```

This would basically mean it can't be executed in parallel and one should always prefer reduce over reduceLeft/Right if possible?