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+Indexing
+========
+
+.. module:: fun
+
+This section contains functions to find elements by its values.
+
+.. function:: index(x, gen, param, state)
+              iterator:index(x)
+
+   :param x: a value to find
+   :returns: the position of the first element that equals to the **x**
+
+   The function returns the position of the first element in the given iterator
+   which is equal (using ``==``) to the query element, or ``nil`` if there is
+   no such element.
+
+   Examples:
+
+   .. code-block:: lua
+
+    > print(index(2, range(0)))
+    nil
+
+    > print(index("b", {"a", "b", "c", "d", "e"}))
+    2
+
+.. function:: index_of(x, gen, param, state)
+              iterator:index_of(x)
+
+   An alias for :func:`index`.
+
+.. function:: elem_index(x, gen, param, state)
+              iterator:elem_index(x)
+
+   An alias for :func:`index`.
+
+.. function:: indexes(x, gen, param, state)
+              iterator:indexes(x)
+
+   :param x: a value to find
+   :returns: an iterator which positions of elements that equal to the **x**
+
+   The function returns an iterator to positions of elements which equals to 
+   the query element.
+
+   Examples:
+
+   .. code-block:: lua
+
+    > each(print, indexes("a", {"a", "b", "c", "d", "e", "a", "b", "a", "a"}))
+    1
+    6
+    9
+    10
+
+   .. seealso:: :func:`filter`
+
+.. function:: indices(x, gen, param, state)
+              iterator:indices(x)
+
+   An alias for :func:`indexes`.
+
+.. function:: elem_indexes(x, gen, param, state)
+              iterator:elem_indexes(x)
+
+   An alias for :func:`indexes`.
+
+.. function:: elem_indices(x, gen, param, state)
+              iterator:elem_indices(x)
+
+   An alias for :func:`indexes`.
+
+