There is the basic programming language, which provides a set of instructions that computer would do; then there is the meta-language (e.g. macros, templates) t

There is the basic programming language, which provides a set of instructions that computer would do; then there is the meta-language (e.g. macros, templates) that provides instructions to compose instructions. I have come to realize that the functional programming essentially is the latter part. For example, I have a meta language in which we can define a box and unbox: subcode: box_a instructions that un-boxes a type ... BLOCK instructions that boxes a type ... subcode: box_b instructions that un-boxes b type ... BLOCK instructions that boxes b type ... main_code: &call box_a &call box_b your code That is a verbose version of J's under adverb with my meta-layer that I can use in any languages (C, Python, ...).