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
- FAILURE CONDITIONS
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
- SEE ALSO
++, |||, >>, a, atleast, elistof, finished, fix, listof, many, nothing,
possibly, rightbin, some.