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\DOC listof
\TYPE {listof : ('a -> 'b * 'c) -> ('c -> 'd * 'a) -> string -> 'a -> 'b list * 'c}
\SYNOPSIS
Parses a separated list of items.
\DESCRIBE
If {p} is a parser for ``items'' of some kind, {s} is a parser for a
``separator'', and {e} is an error message, then {listof p s e} parses a
nonempty list of successive items using {p}, where adjacent items are separated
by something parseable by {s}. If a separator is parsed successfully but there
is no following item that can be parsed by {s}, an exception {Failure e} is
raised. (So note that the separator must not terminate the final element.)
\FAILURE
The call {listof p s e} itself never fails, though the resulting parser may.
\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, many, nothing,
possibly, rightbin, some.
\ENDDOC
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