Information that might be of interest to someone here:

The formal name for the “empty” binary infix operator that gets implied in the AST when doing this, is the “juxtaposition” (or “juxtapose”, or “juxt”) operator. The implicit multiplication operator between `3` and `a` in the polynomial expression `3a + 4`, and the implicit function-application operator in the Lambda-calculus expression `f x y`, are both instances of an implied juxtaposition operator (with different semantics for it in each of the two cases, as befits each type of algebra/calculus.)