Jpye at 23:49, 13 December 2010

2010-12-13T23:49:17Z

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	r = D/2.;</source>		r = D/2.;</source>
	The ALIASES statement differs from the [[ARE_THE_SAME]] statement in that the equivalence between the two variables is established at the same time as the new variable is named, which makes things simpler from the point of view of building up the model's [[Instance hierarchy]].		The ALIASES statement differs from the [[ARE_THE_SAME]] statement in that the equivalence between the two variables is established at the same time as the new variable is named, which makes things simpler from the point of view of building up the model's [[Instance hierarchy]].


	See also [[IS_A\|'''IS_A''']], [[IS_REFINED_TO]] and [[WILL_BE]].		See also [[IS_A\|'''IS_A''']], [[IS_REFINED_TO]] and [[WILL_BE]].
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	== ALIASES with arrays ==		== ALIASES with arrays ==

	''The following information comes from the ASCEND Manual (see [[Category:Documentation]])''		''The following information comes from the ASCEND Manual (see [[:Category:Documentation]])''

	More complex ALIASES statements are possible. We can take a set of <tt>symbol_constant</tt> or <tt>integer_constant</tt> and pair it with a list of instances to create an array. For the moment, the syntax and semantics is as follows:		More complex ALIASES statements are possible. We can take a set of <tt>symbol_constant</tt> or <tt>integer_constant</tt> and pair it with a list of instances to create an array. For the moment, the syntax and semantics is as follows:
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	ALIASES/'''IS_A''' can be used inside a [[FOR]] statement. When this occurs, the definition of <tt>aset</tt> must be indexed and it must be the last subscript of <tt>alias_array_instance</tt>. The statement must look like:		ALIASES/'''IS_A''' can be used inside a [[FOR]] statement. When this occurs, the definition of <tt>aset</tt> must be indexed and it must be the last subscript of <tt>alias_array_instance</tt>. The statement must look like:


	<source lang="a4c">alias_array_instance[FOR_index][aset[FOR_index]] ALIASES (list_of_instances) WHERE aset[FOR_index] IS_A set OF settype WITH_VALUE value_list_matching_settype);</source>		<source lang="a4c">alias_array_instance[FOR_index][aset[FOR_index]] ALIASES (list_of_instances) WHERE aset[FOR_index] IS_A set OF settype WITH_VALUE value_list_matching_settype);</source>
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	These tricks with ALIASES can be especially useful when [[Plotting in ASCEND]].		These tricks with ALIASES can be especially useful when [[Plotting in ASCEND]].

			[[Category:Documentation]]


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

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The '''ALIASES''' statement is used to create a local alias of another variable elsewhere in an ASCEND model. You might for example have a complicated [[Object-oriented_modelling|object-oriented model]] containing some important variables nested in a sub-[[MODEL]]. Using an ALIASES statement you can pull out that nested variable and make it more visible by being available in your top-level model.

<source lang="a4c">pipe IS_A pipe_model;
D ALIASES pipe.diameter;

r IS_A distance;
r = D/2.;</source>
The ALIASES statement differs from the [[ARE_THE_SAME]] statement in that the equivalence between the two variables is established at the same time as the new variable is named, which makes things simpler from the point of view of building up the model's [[Instance hierarchy]].

See also [[IS_A|'''IS_A''']], [[IS_REFINED_TO]] and [[WILL_BE]].

== ALIASES with arrays ==

''The following information comes from the ASCEND Manual (see [[Category:Documentation]])''

More complex ALIASES statements are possible. We can take a set of <tt>symbol_constant</tt> or <tt>integer_constant</tt> and pair it with a list of instances to create an array. For the moment, the syntax and semantics is as follows:

<source lang="a4c">alias_array_instance[aset] ALIASES (list_of_instances) WHERE aset IS_A set OF settype;</source>

or

<source lang="a4c">alias_array_instance[aset] ALIASES (list_of_instances) WHERE aset IS_A set OF settype WITH_VALUE (value_list_matching_settype);</source>
<tt>aset</tt> is the name of the set that will be created by the '''IS_A''' to index the array of aliases. If <tt>value_list_matching_set_type</tt> is not given, the compiler will make one up out of the integers (1..number of names in <tt>list_of_instances</tt>) or symbols derived from the individual names given. If the value list is given, it must have the
same number of elements as the list of instances does. The value list elements must be unique because they form a set. The list of instances can contain duplicates. If any of these conditions are not met properly, the statement is in error.

ALIASES/'''IS_A''' can be used inside a [[FOR]] statement. When this occurs, the definition of <tt>aset</tt> must be indexed and it must be the last subscript of <tt>alias_array_instance</tt>. The statement must look like:

<source lang="a4c">alias_array_instance[FOR_index][aset[FOR_index]] ALIASES (list_of_instances) WHERE aset[FOR_index] IS_A set OF settype WITH_VALUE value_list_matching_settype);</source>

Here, as with the unindexed version, the [[WITH_VALUE]] portion is optional.

If this explanation is unclear, just try it out. The compiler error messages for ALIASES/'''IS_A''' are particularly good because we know it is a bit tricky to explain.

These tricks with ALIASES can be especially useful when [[Plotting in ASCEND]].

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

ALIASES - Revision history

Jpye at 23:49, 13 December 2010

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