The pure vs. impure stuff is a red herring. It's meant to throw you off the scientific trail. If there are merits to the FP approach, as there are, then one or two drawbacks in a few of the languages aren't a problem. If there are multiple problems with the FP approach, then we discard it and toss out the languages that use it or modify them to only use the useful subset of that approach.

With what little information we have in this example, it would be best to modify the language so that it includes those two low-level functions in its specifications and make those global variables they require.

Modifying the language spec...is that pure or impure I wonder?

>Modifying the language spec...is that pure or impure I wonder?

Neither, it's completely orthogonal to the pure/impure distinction.

Remember that the "FP approach" can be used in so-called "imperative" languages too. The reverse isn't as true.

The reverse is true. Just modify the language. I don't see why people are insisting on this "purity" in approaches. It's obviously leading to difficulties.

Pure has a specific technical meaning here relating to the absence of side effects.

http://en.wikipedia.org/wiki/Pure_function