Red and Rebol have prefix notation and no parentheses to delimit the arguments. That means you have to know the arity of each function to understand how to buil

Red and Rebol have prefix notation and no parentheses to delimit the arguments. That means you have to know the arity of each function to understand how to build the parse tree. This is apparently not as hard as it sounds, because natural languages work the same way, although they can be ambiguous, at least if you're familiar with all the functions.