Numbers Index
=============

Given a list of integer numbers we wish to know the numbers whose position matches themselves.
You are required to deliver the following functions in the module :mod:`numindex` (file :file:`numindex.py`).

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The first function is:

    .. py:function:: numindex_for(l)

such that

    **given** *l*, a :class:`list` of :class:`int`

    **returns** a new :class:`list` of :class:`int` with any number in ``l`` whose position is equal to itself. They are arrange the same as in ``l``.

For example:

    .. literalinclude:: numindex_for.test
        :language: python3
        :start-after: --ini
        :end-before: --fi

Observe that in the first example, positions 0, 3, 6 of list ``l`` have a 0, a 3 and a 6 respectively.

.. warning::
    This function must be implement using the **for** sentence.

Doctests are available in the :download:`numindex_for.test` file.

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The second function is:

    .. py:function:: numindex_cl(l)

with the same specification as numindex but it must be implemented using **comprehension lists**.

.. warning::
    This function must be implement using **comprehension lists**.


Doctests are available in the :download:`numindex_cl.test` file.