J Notation as a Tool of Thought
This seems very interesting for numerical computation, but at first glance few of these operations seem to apply directly to general computation (I&#x27;m sure that there are isomorphisms that can be used to apply them indirectly).<p>The example with sorting was the oddest from this point of view. The author praised the idea of the permutation vector  as being a relatively direct mathematical specification of sorting (return the permutation of the original array in sorted order) while leaving out the &#x27;sorted&#x27; part. Also, this focuses entirely on the result, but there is no word on the algorithm - &#x27;<i>how</i> is the array sorted&#x27; is the question that computer science is designed to solve, as opposed to &#x27;what are the fixed points of a sorted array&#x27;.<p>As such, as someone with no experience of J, I&#x27;m left wondering if this is another example of the infamous Haskell quicksort - well-picked examples of code which produces a desired result are extraordinarily terse and expressive, but actually implementing well-known algorithms is often just as verbose as C, give or take.