
.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "examples/indented_tree.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Click :ref:`here <sphx_glr_download_examples_indented_tree.py>`
        to download the full example code

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_examples_indented_tree.py:


Parsing Indentation
===================

A demonstration of parsing indentation (“whitespace significant” language)
and the usage of the Indenter class.

Since indentation is context-sensitive, a postlex stage is introduced to
manufacture INDENT/DEDENT tokens.

It is crucial for the indenter that the NL_type matches
the spaces (and tabs) after the newline.

.. GENERATED FROM PYTHON SOURCE LINES 14-56

.. code-block:: default

    from lark import Lark
    from lark.indenter import Indenter

    tree_grammar = r"""
        ?start: _NL* tree

        tree: NAME _NL [_INDENT tree+ _DEDENT]

        %import common.CNAME -> NAME
        %import common.WS_INLINE
        %declare _INDENT _DEDENT
        %ignore WS_INLINE

        _NL: /(\r?\n[\t ]*)+/
    """

    class TreeIndenter(Indenter):
        NL_type = '_NL'
        OPEN_PAREN_types = []
        CLOSE_PAREN_types = []
        INDENT_type = '_INDENT'
        DEDENT_type = '_DEDENT'
        tab_len = 8

    parser = Lark(tree_grammar, parser='lalr', postlex=TreeIndenter())

    test_tree = """
    a
        b
        c
            d
            e
        f
            g
    """

    def test():
        print(parser.parse(test_tree).pretty())

    if __name__ == '__main__':
        test()



.. rst-class:: sphx-glr-timing

   **Total running time of the script:** ( 0 minutes  0.000 seconds)


.. _sphx_glr_download_examples_indented_tree.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download sphx-glr-download-python

     :download:`Download Python source code: indented_tree.py <indented_tree.py>`



  .. container:: sphx-glr-download sphx-glr-download-jupyter

     :download:`Download Jupyter notebook: indented_tree.ipynb <indented_tree.ipynb>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_
