One of the virtues of J is its conciseness; I think this is underrated in exploratory programming. Here I present some J one-liners alongside samples of other languages.
Here I'd like to show an example of runtime complexity, arising from a practical problem.
A question in compiler design is: what optimizations should a given compiler perform? Optimizations for functional languages in particular are not well-known; it is not obvious which optimizations will provide the greatest speedup on user code.
The totient function is defined for positive integers as:prev | next