.. _constantDoc:

.. index:: single: constant

==============
Constant Block
==============

Declares a **constant block** or a **constant block bundle** using the keyword ``constant``.

* Declaration_
* `Shorthand Declaration`_
* `Ports Table`_
* Description_
* `Code Examples`_

.. figure:: Images/ConstantBlock.png
   :scale: 100%
   :alt: Signal Block
   :align: center

----

Declaration
===========

::
	
	# constant block
	constant LABEL {
		value: 	none 
		meta:	none
	}
	
	# constant block bundle
	constant LABEL [SIZE] {
		value: 	none
		meta:	none
	}

**LABEL**
	:definition:	the label of the block
	
**SIZE**
	:definition:	the size of the block bundle
	:type:			constant integer port (CIP)
	
----
	
Shorthand Declaration
=====================

::

	# constant block
	BasicType >> LABEL;
	
	# constant block bundle
	BasicTypeList >> LABEL;

**LABEL**
	:definition:	the label of the block
	
**BasicType**
	:definition:	an :ref:`integer <Integer>`, a :ref:`real <Real>`, or a :ref:`string <String>`
	
**BasicTypeList**
	:definition:	a list of :ref:`integer <Integer>`, a list of :ref:`real <Real>`, or a list of :ref:`string <String>`

----

Ports Table 
===========

+------+-----------+-----------+--------------------------+------------+------------+---------------+---------------+
|      |           |           |                          |            |            |               |               |
+------+-----------+-----------+--------------------------+------------+------------+---------------+---------------+
| Port | Name      | Direction | Type                     | Connection | Access     | Default       | Required      | 
+======+===========+===========+==========================+============+============+===============+===============+
| 1    | output    | output    | CIP, CRP, CSP :sup:`(2)` | multiple   | LABEL >>   | ``none``      | no :sup:`(1)` |
|      |           |           |                          |            +------------+               |               |
|      |           |           |                          |            | assignment |               |               |
+------+-----------+-----------+--------------------------+------------+------------+---------------+---------------+
| 2    | ``value`` | input     | CIP, CRP, CSP            | single     | >> LABEL   | ``none``      | yes           |
|      |           |           |                          |            +------------+               |               |
|      |           |           |                          |            | property   |               |               |
+------+-----------+-----------+--------------------------+------------+------------+---------------+---------------+
| 3    | ``meta``  | input     | CSP                      | single     | property   | ``none``      | no            |
+------+-----------+-----------+--------------------------+------------+------------+---------------+---------------+

**CIP**
	constant integer port
	
**CRP**
	constant real port

**CSP**
	constant string port
	
:sup:`1` Warning issued during compilation if the port is left unconnected.

:sup:`2` The port's type is the same as ``value`` port's type.

----

Description
===========

A ``constant`` block can be assigned one of the :ref:`basic types<basicTypesDoc>`. Its ``value`` is assigned during declaration. Its ``output`` port type is the same as its ``value`` port type.

----

Code Examples
=============

The following code declares a ``constant`` block called 'SamplingRate'. The ``value`` property is assigned an :ref:`Integer`. The output port type of the block is `constant integer`.

::
	
	constant SamplingRate {
		value: 	2048
		meta:	'The sampling rate for analog input.' 
	}
	
	# Shorthand Declaration
	2048 >> SamplingRate;

	
The following code declares a ``constant`` block called 'StandardPitch'. The ``value`` property is assigned a :ref:`Real`. The output port type of the block is `constant real`.

::

	constant StandardPitch {
		value: 	440.0
		meta:	'The musical pitch for all instrument.' 
	}

	# Shorthand Declaration
	440.0 >> StandardPitch;
	
The following code declares a ``constant`` block called 'OutgoingIP'. The ``value`` property is assigned a :ref:`String`. The output port type of the block is `constant string`.

::

	constant OutgoingIP {
		value: 	'192.168.1.13'
		meta:	'The IP address of the server.' 
	}
	
	# Shorthand Declaration
	'192.168.1.13' >> OutgoingIP;
	
	

The following code declares a ``constant`` block bundle called 'Frequencies'. The ``value`` property is assigned a :ref:`Real` list. The output port type of the block is `constant real`.

::

	constant Frequencies [2] {
		value: 	[440.0, 880.0]
		meta:	'Frequencies of A4 and A5.' 
	}

	# Shorthand Declaration
	[440.0, 880.0] >> Frequencies;