leftbin : ('a -> 'b * 'c) -> ('c -> 'd * 'a) -> ('d -> 'b -> 'b -> 'b) -> string -> 'a -> 'b * 'c

Parses iterated left-associated binary operator.

If p is a parser for ``items'' of some kind, s is a parser for some ``separator'', c is a `constructor' function taking an element as parsed by s and two other elements as parsed by p and giving a new such element, and e is an error message, then leftbin p s c e will parse an iterated sequence of items by p and separated by something parsed with s. It will repeatedly apply the constructor function c to compose these elements into one, associating to the left. For example, the input:
meaning successive segments pi that are parsed by p and sj that are parsed by s, will result in
  c (c s2 (c s1 p1 p2) p3) p4

The call leftbin p s c e never fails, though the resulting parser may.

This is one of a suite of combinators for manipulating ``parsers''. A parser is simply a function whose OCaml type is some instance of :('a)list -> 'b * ('a)list. The function should take a list of objects of type :'a (e.g. characters or tokens), parse as much of it as possible from left to right, and return a pair consisting of the object derived from parsing (e.g. a term or a special syntax tree) and the list of elements that were not processed.

++, ||, >>, a, atleast, elistof, finished, fix, listof, many, nothing, possibly, rightbin, some.