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JakeWheat/intro_to_parsing

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Intro to Parsing with Parsec in Haskell

Overview

WIP, a tutorial which demonstrates the basics of Parsec and goes on to build a SQL query parser.

You can view this tutorial as HTML online here:

and you can view the files directly in the github repository here:

Summary of sections

Introduction to parsing with Parsec, including a review of Text.Parsec.Char functions.

Creating a very simple expression language parser, and introducing some functions from Text.Parsec.Combinator.

Rewriting the simple expression parser code in a more succinct style.

Review and examples of all functions from Text.Parsec.Combinator, and some from Control.Applicative and Control.Monad.

The utility functions used in the previous tutorials, plus some notes on types in Parsec.

This covers using the Text.Parsec.Expr for expression parsing with prefix, postfix and infix operators with fixity.

Looks at an issue we have with the way the symbol parser in the Text.Parsec.Expr tutorial was used, and some possible fixes.

This covers the Text.Parsec.Perm module which is used for parsing different things in flexible order.

This covers Text.Parsec.Token which can be used to create token parsers easily.

This covers building a parser a subset of value expressions from SQL, which are an extension of the simple expression types and parsers covered in previous tutorials.

This covers building a parser to parse query expressions with select lists, simple from, where, group by, having and order by.

This extend the parser for query expressions to support a from clause with much more features including joins.

Here is the code from ValueExpressions, QueryExpressions and FromClause plus tests put together and rearranged as a coherent standalone module.

This quick module covers a simple pretty printer for our SQL ast.

In this document, we will explore error messages with parsec and how restructuring parser code can lead to better or worse error messages.

Going further

If you are interesting in SQL parsing, check out the project to build a complete SQL parser here: http://jakewheat.github.io/simple-sql-parser/latest. The parsing code in the simple-sql-parser project is based on this tutorial code.

Extras

an executable which contains the boilerplate to run a parsec parser on a string passed as an argument

an executable which contains the boilerplate to run a parsec parser on a file passed as an argument

Contact: jakewheatmail@gmail.com

License: BSD3