More idiomatic K solution

[jaredkrinke]

@JohnEarnest provided some suggestions for simplifying the K solution:

You can simplify the definition:

fact:{*/1+!x}

by observing that the lambda serves only to consume a single rightmost argument, and instead write it in tacit form, which some people find prettier:

fact:*/1+!:

You can also replace the lambda containing a conditional applied to each element of a list:

{$[x>1000000;1;0]}'

With applying the comparison operator to the entire input vector, yielding a vector of booleans:

1000000<

John also clarified the meaning of the colon at the end of the fact definition for me:

a colon suffix on a verb forces its monadic interpretation, especially in the context of an adverb. Otherwise, the terminal verb in a composition- and thus the composition itself- is "ambivalent" (i.e. "both valences"); adverbs prefer the dyadic interpretation, which can lead to surprises. It isn't strictly necessary for this application but it does clarify intent to a reader.

Thanks, John!