In computer programming, combinator parsing is a technique for constructing parsers using parser combinators. A parser combinator is a higher-order function that accepts several parsers as input and returns a new parser as its output. This allows parsers to be composed in a modular way, making it easy to construct complex parsers from simpler ones.

Parser combinators are typically implemented using higher-order functions in a functional programming language. This allows parsers to be expressed in a natural way, using the same syntax as the grammar they are parsing. For example, the following code defines a parser for the expression x + y:

Code snippet
def parser(x):
  return parse_integer(x)

def parser(y):
  return parse_integer(y)

def parser(x, y):
  return parse_binop("+", parser(x), parser(y))
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This code defines three parsers: parser(x), parser(y), and parser(x, y). The parser(x) parser parses an integer from the input string. The parser(y) parser parses another integer from the input string. The parser(x, y) parser parses the expression x + y. It does this by first calling the parser(x) parser to parse the first integer, and then calling the parser(y) parser to parse the second integer. Finally, it calls the parse_binop() parser to combine the two integers into an expression.

Parser combinators can be used to construct parsers for any kind of grammar. They are particularly well-suited for parsing grammars that are recursive or ambiguous. Parser combinators are also relatively easy to implement and use, making them a popular choice for parsing in functional programming languages.

Here are some of the benefits of using parser combinators:

They are modular and reusable. Parsers can be composed from simpler parsers, making it easy to construct complex parsers from a small number of basic building blocks.
They are expressive. Parsers can be expressed in a natural way, using the same syntax as the grammar they are parsing.
They are efficient. Parser combinators can be implemented in a variety of ways, including using backtracking or memoization.
If you are interested in learning more about parser combinators, there are a number of resources available online. A good place to start is the Wikipedia article on parser combinators: https://en.wikipedia.org/wiki/Parser_combinator. You can also find a number of parser combinator libraries available for different programming languages.