> If you like, you can think of unwords . words as an orthogonal projection onto the subspace of strings on which unwords is a genuine left-inverse of words (cf

> If you like, you can think of unwords . words as an orthogonal projection onto the subspace of strings on which unwords is a genuine left-inverse of words (cf. Moore-Penrose pseudoinverses). It's even more like a reflector in a https://en.wikipedia.org/wiki/Reflective_subcategory https://en.wikipedia.org/wiki/Reflective_subcategory. (To make this analogy precise, you'd have to have some category structure where single-space is initial among all whitespace strings. Which is certainly possible; you just have to persuade yourself that that's a natural thing to do.)