\DOC ++

\TYPE {(++) : ('a -> 'b * 'c) -> ('c -> 'd * 'e) -> 'a -> ('b * 'd) * 'e}

\SYNOPSIS
Sequentially compose two parsers.

\DESCRIBE
If {p1} and {p2} are two parsers, {p1 ++ p2} is a new parser that parses as
much of the input as possible using {p1} and then as much of what remains using
{p2}, returning the pair of parse results and the unparsed input.

\FAILURE
Never fails.

\COMMENTS
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.

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

\ENDDOC