Difference between revisions of "Var"

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(Fix errors and simplify (invalid doc references still need fixing))
(insert link to declaration)
 
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{{Var}}
 
{{Var}}
  
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Var is a [[keyword]] used to mark the section where [[Variable|variables]] and their data [[Type|type]]s are declared. When used for a parameter of a [[Procedure|procedure]] or [[Function|function]] then '''var''' indicates the use of a [[Variable parameter|variable parameter]].
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The [[Keyword|keyword]] <syntaxhighlight lang="pascal" inline>var</syntaxhighlight> is used to:
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* start section of [[Variable|variable]] declarations, and
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Variables are typically declared at the beginning of a [[program]], [[procedure]], [[function]] or [[Unit|unit]].
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* declare a formal parameter as penetrating mutable.
  
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<syntaxhighlight>var
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== Variable declaration section ==
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  age: integer;</syntaxhighlight>  
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In a [[Block|block]] the word <syntaxhighlight lang="pascal" inline>var</syntaxhighlight> starts a section of one or more variable [[Declaration|declarations]].
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<syntaxhighlight lang="pascal" highlight="1">
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var
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age: integer;
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</syntaxhighlight>
  
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If you are planning to use various variables of the same type, they can be grouped so they share the same type definition. The variables must be separated by a [[comma]].
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Variables bearing the same [[Type|data type]] can be grouped, by separating their respective [[Identifier|identifiers]] by a [[Comma|comma]]:
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<syntaxhighlight lang="pascal" highlight="2">
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var
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firstName, lastName, address: string;
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</syntaxhighlight>
  
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<syntaxhighlight>var
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== Variable parameter ==
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  FirstName, LastName, address: string;</syntaxhighlight>  
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The word <syntaxhighlight lang="pascal" inline>var</syntaxhighlight> prior a formal parameter declaration indicates that this [[Variable parameter|parameter is variable]], that means assigning values to it will affect the named parameter at the call site.
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<syntaxhighlight lang="pascal" highlight="1">
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procedure censor(var xxx: longWord);
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begin
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if (xxx = $4655434B) or (xxx = $6675636B) then
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begin
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xxx := $2A2A2A2A;
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end;
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end;
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</syntaxhighlight>
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After invoking <syntaxhighlight lang="pascal" inline>procedure censor</syntaxhighlight> the value of the variable that was supplied at the call site (i. e. where the procedure was called) will (possibly) have changed, too.
  
 
== See also ==
 
== See also ==
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* [[Local variables]]
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* [[Const|<syntaxhighlight lang="pascal" inline>const</syntaxhighlight>]]
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* [[Global variables]]
 
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* [[doc:ref/refse19.html#x49-540004.2|Variable declaration]]
 
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* [[doc:ref/refse21.html#x51-560004.4|Thread Variables]]
 
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[[category:Pascal]]
 

Latest revision as of 22:14, 4 July 2021

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The keyword var is used to:

  • start section of variable declarations, and
  • declare a formal parameter as penetrating mutable.

Variable declaration section

In a block the word var starts a section of one or more variable declarations. 

var
	age: integer;

Variables bearing the same data type can be grouped, by separating their respective identifiers by a comma: 

var
	firstName, lastName, address: string;

Variable parameter

The word var prior a formal parameter declaration indicates that this parameter is variable, that means assigning values to it will affect the named parameter at the call site. 

procedure censor(var xxx: longWord);
begin
	if (xxx = $4655434B) or (xxx = $6675636B) then
	begin
		xxx := $2A2A2A2A;
	end;
end;

After invoking procedure censor the value of the variable that was supplied at the call site (i. e. where the procedure was called) will (possibly) have changed, too.

See also

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