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+Operators
+=========
+
+.. module:: fun.operator
+
+This auxiliary module exports a set of Lua operators as intrinsic functions
+to use with the library high-order primitives.
+
+.. contents::
+
+.. note:: **op** can be used as a shortcut to **operator**.
+
+Comparison operators
+--------------------
+
+.. seealso:: `Lua Relational Operators
+              <http://www.lua.org/manual/5.2/manual.html#3.4.3>`_
+
+.. function:: le(a, b)
+
+   :returns: **a** <= **b**
+
+.. function:: lt(a, b)
+
+   :returns: **a** < **b**
+
+.. function:: eq(a, b)
+
+   :returns: **a** == **b**
+
+.. function:: ne(a, b)
+
+   :returns: **a** ~= **b**
+
+.. function:: ge(a, b)
+
+   :returns: **a** >= **b**
+
+.. function:: gt(a, b)
+
+   :returns: **a** > **b**
+
+Arithmetic operators
+--------------------
+
+.. seealso:: `Lua Arithmetic Operators 
+              <http://www.lua.org/manual/5.2/manual.html#3.4.1>`_
+
+.. function:: add(a, b)
+
+   :returns: **a** + **b**
+
+.. function:: div(a, b)
+
+    An alias for :func:`truediv`.
+
+.. function:: truediv(a, b)
+
+   :returns: **a** / **b**
+
+   Performs "true" float division.
+   Examples:
+
+   .. code-block:: lua
+
+    > print(operator.div(10, 3))
+    3.3333333333333
+    > print(operator.div(-10, 3))
+    -3.3333333333333
+
+.. function:: floordiv(a, b)
+
+   :returns: math.floor(**a** / **b**)
+
+   Performs division where a result is rounded down. Examples:
+
+   .. code-block:: lua
+
+    > print(operator.floordiv(10, 3))
+    3
+    > print(operator.floordiv(12, 3))
+    4
+    > print(operator.floordiv(-10, 3))
+    -4
+    > print(operator.floordiv(-12, 3))
+    -4
+
+.. function:: intdiv(a, b)
+
+   Performs C-like integer division.
+
+   Equvalent to:
+
+   .. code-block:: lua
+
+    function(a, b)
+        local q = a / b
+        if a >= 0 then return math.floor(q) else return math.ceil(q) end
+    end
+
+   Examples:
+
+   .. code-block:: lua
+
+    > print(operator.floordiv(10, 3))
+    3
+    > print(operator.floordiv(12, 3))
+    4
+    > print(operator.floordiv(-10, 3))
+    -3
+    > print(operator.floordiv(-12, 3))
+    -4
+
+.. function:: mod(a, b)
+
+   :returns: **a** % **b**
+
+   .. note:: Result has same sign as **divisor**. Modulo in Lua is defined as
+             ``a % b == a - math.floor(a/b)*b``.
+
+   Examples:
+
+   .. code-block:: lua
+    :emphasize-lines: 5-6
+
+    > print(operator.mod(10, 2))
+    0
+    > print(operator.mod(10, 3))
+    2
+    print(operator.mod(-10, 3))
+    2 -- == -1 in C, Java, JavaScript and but not in Lua, Python, Haskell!
+
+.. function:: neq(a)
+
+   :returns: -**a**
+
+.. function:: unm(a)
+
+   Unary minus. An alias for :func:`neq`.
+
+.. function:: pow(a, b)
+
+   :returns: math.pow(**a**, **b**)
+
+.. function:: sub(a, b)
+
+   :returns: **a** - **b**
+
+String operators
+----------------
+
+.. seealso:: `Lua Concatenation Operator
+              <http://www.lua.org/manual/5.2/manual.html#3.4.5>`_
+
+.. function:: concat(a, b)
+
+   :returns: **a** .. **b**
+
+.. function:: len(a)
+
+   :returns: # **a**
+
+.. function:: length(a)
+
+   An alias for :func:`len`.
+
+Logical operators
+-----------------
+
+.. seealso:: `Lua Logical Operators
+              <http://www.lua.org/manual/5.2/manual.html#3.4.4>`_
+
+.. function:: land(a, b)
+
+   :returns: **a** and **b**
+
+.. function:: lor(a, b)
+
+   :returns: **a** or **b**
+
+.. function:: lnot(a)
+
+   :returns: not **a**
+
+.. function:: truth(a)
+
+   :returns: not not **a**
+
+   Return ``true`` if **a** is true, and ``false`` otherwise. Examples:
+
+   .. code-block:: lua
+
+    > print(operator.truth(1))
+    true
+    > print(operator.truth(0))
+    true -- It is Lua, baby!
+    > print(operator.truth(nil))
+    false
+    > print(operator.truth(""))
+    true
+    > print(operator.truth({}))
+    true
+