fpinscala/fpinscala — pull request #343 by mosesn (2014-12-01 08:13:47+00:00)
Title: fpinscala-parallelism: Explains that the example map2 is semantically incorrect

Problem
======
The function returned by the example map2 waits for the underlying Futures to be finished before returning. This means that
```scala
exampleMap2(fork(par1), fork(par2), fn)
```
Will block and wait for fork to be finished for both of them.

Solution
======
Clarify the comment. Providing a correct implementation is tantamount to solving the exercise, which would be a waste.

Extra
====
Fixed a memory visibility bug.