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\DOC nothing
\TYPE {nothing : 'a -> 'b list * 'a}
\SYNOPSIS
Trivial parser that parses nothing.
\DESCRIBE
The parser {nothing} parses nothing: it returns the empty list as its parsed
item and all the input as its unparsed input.
\FAILURE
Never fails.
\USES
This can be useful in alternations (`{|||}') with other parsers producing a list
of items.
\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,
possibly, rightbin, some.
\ENDDOC
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