Difference between revisions of "Var"
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{{Var}} | {{Var}} | ||
− | '''Var''' is a [[Keyword|keyword]] used to mark the section where [[Variable|variables]] and their data [[Type|type]]s are declared. | + | '''Var''' is a [[Keyword|keyword]] that is used for two different purposes: |
− | + | * signify the start of a variable definition section | |
− | Variables are typically declared at the beginning of a [[Program|program]], [[Procedure|procedure]], [[Function|function]] or [[Unit|unit]]. | + | * make a function or procedure parameter be passed by reference instead of passed by value |
+ | |||
+ | == Variable Definition == | ||
+ | Var is used to mark the section where [[Variable|variables]] and their data [[Type|type]]s are declared. Variables are typically declared at the beginning of a [[Program|program]], [[Procedure|procedure]], [[Function|function]] or [[Unit|unit]]. | ||
<syntaxhighlight> | <syntaxhighlight> | ||
Line 17: | Line 20: | ||
</syntaxhighlight> | </syntaxhighlight> | ||
− | + | == Pass by Reference == | |
+ | |||
+ | When used before a parameter of a [[Procedure|procedure]] or [[Function|function]] '''var''' indicates that the parameter is a [[Variable parameter|variable parameter]]. A variable parameter can be used to receive data from, as well as send data to, a procedure or function: | ||
+ | |||
<syntaxhighlight> | <syntaxhighlight> | ||
procedure foo( var v1: sometype; out v2: sometype; const v3: sometype ) | procedure foo( var v1: sometype; out v2: sometype; const v3: sometype ) | ||
begin | begin | ||
− | v1 := v1 + v3; // input and return | + | v1 := v1 + v3; // input and return value |
− | v2 := v3; // only return value | + | v2 := v3; // only return value |
v3 := myconst; // immutable... only input | v3 := myconst; // immutable... only input | ||
end; | end; |
Revision as of 18:03, 17 July 2016
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Var is a keyword that is used for two different purposes:
- signify the start of a variable definition section
- make a function or procedure parameter be passed by reference instead of passed by value
Variable Definition
Var is used to mark the section where variables and their data types are declared. Variables are typically declared at the beginning of a program, procedure, function or unit.
var
age: integer;
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.
var
FirstName, LastName, address: string;
Pass by Reference
When used before a parameter of a procedure or function var indicates that the parameter is a variable parameter. A variable parameter can be used to receive data from, as well as send data to, a procedure or function:
procedure foo( var v1: sometype; out v2: sometype; const v3: sometype )
begin
v1 := v1 + v3; // input and return value
v2 := v3; // only return value
v3 := myconst; // immutable... only input
end;