Jpye at 02:28, 1 June 2010

2010-06-01T02:28:54Z

← Older revision		Revision as of 02:28, 1 June 2010
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	m1, m2, m3 IS_A mass;</source>		m1, m2, m3 IS_A mass;</source>
	Variables in ASCEND can be		Variables in ASCEND can be


	* real-valued solver variables, the most common kind (<tt>solver_var</tt>)		* real-valued solver variables, the most common kind (<tt>solver_var</tt>)
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	Variables can be assigned values in the [[METHOD\|METHODs]] section of a [[MODEL]]:		Variables can be assigned values in the [[METHOD\|METHODs]] section of a [[MODEL]]:


	<source lang="a4c">METHOD values;		<source lang="a4c">METHOD values;
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	END values;</source>		END values;</source>

			See [[Type]]s for the full taxonomy of object types that are available in ASCEND, including relations, sets, arrays, [[MODEL]]s.

	See also [[WILL_BE]], [[equation]], [[Constant]], [[Array\|arrays]].		See also [[WILL_BE]], [[equation]], [[Constant]], [[Array\|arrays]].




	[[Category:Documentation]]		[[Category:Documentation]]

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In ASCEND, '''variables''' (which we also call '''atoms''') must be declared before they can be used. Variables are declared using the [[IS_A]] statement:

<source lang="a4c">x IS_A solver_var;
L IS_A distance;
h IS_A specific_enthalpy;

m1, m2, m3 IS_A mass;</source>
Variables in ASCEND can be

* real-valued solver variables, the most common kind (<tt>solver_var</tt>)
* boolean variables (TRUE or FALSE)
* symbol variables
* integer variables

Although ASCEND can handle all of these types of variables, in practise most [[solvers]] only provide support for solving systems of real-valued variables. We have [[CMSlv]] which provides support for [[conditional modelling]], allowing some degree of mixed integer/boolean/symbol and real-valued equation systems.

Variables can be assigned values in the [[METHOD|METHODs]] section of a [[MODEL]]:

<source lang="a4c">METHOD values;
x := 10;
L := 5.6 {m};

h := 2700 {kJ/kg};
END values;</source>

Variables can have properties, including upper and lower bounds and nominal and default values. These can be accessed in the METHODS section of the model, but can not be used in the equations themselves. Variable properties are considered to be 'metadata'.

<source lang="a4c">METHOD values;
x.lower_bound := 1;
x.upper_bound := 100;

END values;</source>

See also [[WILL_BE]], [[equation]], [[Constant]], [[Array|arrays]].

[[Category:Documentation]]

Variable - Revision history

Jpye at 02:28, 1 June 2010

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