For comparison, [0] is my page on tacit programming in BQN, which is laid out a lot like the OP. It even begins with a filtering example, taking positive entrie

For comparison, [0] is my page on tacit programming in BQN, which is laid out a lot like the OP. It even begins with a filtering example, taking positive entries of a list l with 0⊸<⊸/ l. For odd entries it would be 2⊸|⊸/ and for evens (¬2⊸|)⊸/. APL does have a negation function ~ (not sure why jph hasn't used it), but it has trouble with filtering because / is overloaded to be both a function and an operator[1]. BQN fixes some problems like these in APL, and I'd consider it to be an improvement on both J and APL for tacit programming. [0] https://mlochbaum.github.io/BQN/doc/tacit.html https://mlochbaum.github.io/BQN/doc/tacit.html [1] https://aplwiki.com/wiki/Function-operator_overloading https://aplwiki.com/wiki/Function-operator_overloading