A module to construct indentation aware parsers. Many programming
language have indentation based syntax rules e.g. python and Haskell.
This module exports combinators to create such parsers. This is a
rewrite of the IndentParser package. There are a few changes in the
names of functions besides the underlying code is simplified.

The input source can be thought of as a list of tokens. Abstractly
each token occurs at a line and a column and has a width. The column
number of a token measures is indentation. If t1 and t2 are two tokens
then we say that indentation of t1 is more than t2 if the column
number of occurrence of t1 is greater than that of t2.

Currently this module supports two kind of indentation based syntactic
structures which we now describe:

[Block] A block of indentation /c/ is a sequence of tokens with
indentation at least /c/.  Examples for a block is a where clause of
Haskell with no explicit braces.

[Line fold] A line fold starting at line /l/ and indentation /c/ is a
sequence of tokens that start at line /l/ and possibly continue to
subsequent lines as long as the indentation is greater than /c/. Such
a sequence of lines need to be /folded/ to a single line. An example
is MIME headers. Line folding based binding separation is used in
Haskell as well.

For indentation based grammars notice the following should be true

1. Combinators for skipping whitespace/comments should skip spaces and
comments no matter what the indentation is.

2. All tokenisers of the language should check for indentation. The
combinator `tokeniser` makes its input parser indentation aware. Use
it on all tokenisers of the language.

3. All tokenisers themselves should skip trailing whitespaces and
comments, i.e. they should be lexeme parsers. Otherwise, the will be
problem matching the next token.

A block can then be parsed using the combinator 'blockOf' and a line
fold using 'foldedLinesOf'.

Generating indentation aware tokenisers could be tricky.  One can use
the module "Text.Parsec.IndentParsec.Token" for this.


module Text.Parsec.IndentParsec
       ( module Text.Parsec.IndentParsec.Prim
       , module Text.Parsec.IndentParsec.Combinator
       , module Text.Parsec.IndentParsec.Token
       ) where

import Text.Parsec.IndentParsec.Prim
import Text.Parsec.IndentParsec.Combinator
import Text.Parsec.IndentParsec.Token