Jpye at 22:00, 21 December 2010

2010-12-21T22:00:13Z

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			{{DISPLAYTITLE:IS_A}}
	The '''IS_A''' statement is used to declare a new variable or sub-MODEL in your [[MODEL]].		The '''IS_A''' statement is used to declare a new variable or sub-MODEL in your [[MODEL]].
	<source lang="a4c">x IS_A distance; (* this is an 'atomic' variable: just		<source lang="a4c">x IS_A distance; (* this is an 'atomic' variable: just

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The '''IS_A''' statement is used to declare a new variable or sub-MODEL in your [[MODEL]].
<source lang="a4c">x IS_A distance; (* this is an 'atomic' variable: just
a single numerical value that can be solved for *)
v IS_A vec3; (* vec3 is a sub-model containing x,y,z components *)
v.x = x; (* once variables are declared, you can use them
in relations involving other variables, possibly from your
sum-models *)</source>
'''IS_A''' can also be used to declare [[arrays and sets]].

'''IS_A''' can also be used in [[Parametric_model|parametric models]] to define constants that will be provided during the declaration, for example:

<source lang="a4c">MODEL hxbase (
hotfluid, coldfluid, flowtype IS_A symbol_constant; (* this may have
to be separated. *)
) WHERE (
flowtype IN ['counterflow','coflow']; (* == TRUE; may be needed, i forget *)
);

(*...declaration for a specialisation of hxbase with water as the fluid... *)
MODEL hxwater (
flowtype IS_A symbol_constant;
) REFINES hxbase (
hotfluid :=='water';
coldfluid:=='water';
);

(*...then later...*)
a IS_A hxwater('coflow');</source>

See also [[WILL_BE]], [[IS_REFINED_TO]], [[ALIASES]], [[ARE_THE_SAME]].

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

IS A - Revision history

Jpye at 22:00, 21 December 2010

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