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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
|
