Replace `for` with `cfor` in the Scala code for improved performance

[ColourGrey]

Numerical for loops in Scala are known to be slower than their counterparts in other languages, and also generate more garbage, because they are implemented as a composition of very high-level language constructs; details can be found here and here, for instance. This is why the Spires library provides the cfor macro, which implements loops in a significantly more efficient way.

With the above rationale, would the maintainers of this repository agree to the replacing of for with cfor, for improved performance of the benchmarked Scala code?

[kostya]

We not like such optimizations. We try to use standard language constructs and containers. If for in Scala is slow, is not Scala developers should care about it?

[CoolDalek]

Performance-sensitive code usually switches to either while-loops or tail recursive functions.
To ensure the optimization of tail recursive functions Scala standard library contains @tailrec annotation.

Scala developers usually don't care about for-loops being slow because they are used mostly for monadic binding (i.e. Scala for-comprehensions are analogues of Haskell do-comprehensions and not just loops).