| var | declaration |
| Syntax | A variableDeclaration is one of:
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| Description | A variable declaration creates a new variable (or variables). Only form (a) will be explained here. See collectionDeclaration for explanation of form (b). The typeSpec of form (a) can be omitted only if the initializing value is present.
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| Example |
var j, k : int := 1 % j and k are assigned value 1
var t := "Sample" % The type of t is string
var v : array 1 .. 3 of string ( 6 ) :=
init ( "George", "Fred", "Alice" )
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| Details | The initializing value, if present, must be an expression or else a list of items separated by commas inside init ( … ). The syntax of initializingValue is one of:
Each init ( … ) corresponds to an array, record or union value that is being initialized. These must be nested for initialization of nested types. If the typeSpec is omitted, the variable's type is taken to be the (root) type of the initializing expression, for example, int or string. The typeSpec cannot be omitted for dynamic arrays or when the initializing value is of the form init ( … ). The values inside init ( … ) must be known at compile time. The keyword pervasive can be inserted just after var. When this is done, the variable is visible inside all subconstructs of the variable's scope. Without pervasive, the variable is not visible inside modules unless explicitly imported. Pervasive variables need not be imported. You can abbreviate pervasive as an asterisk (*). OOT extends Turing in the following way. OOT changes form (a) to allow the optional use of the register keyword to request that the variable be placed in a machine register. The OOT syntax for form (a) is actually:
var [pervasive] [register] id { , id } [ : typeSpec ] [ := initializingValue ]
In the current (1994) OOT implementation, programs are run interpretively using pseudo-code, which has no machine registers, and the register keyword is ignored. See register for restrictions on the use of register variables.
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| See also | collection, bind, procedure and function declarations, parameter declarations, export lists and import lists for other uses of the keyword var.
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