| unit | file containing module, monitor, or class |
| Syntax | A compilationUnit is one of:
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| Description | A program can be divided up into units, each in a separate file. All of these files except the main program begin with the keyword unit. The unit contains the main program, a module, a monitor or a class.
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| Example | Here is stack module that is separated out into a file whose name is stack.
unit % The keyword unit begins each separate file
module stack
export push, pop
var top : int := 0
var contents : array 1 .. 100 of int
procedure push ( i : int )
top += 1
contents ( top ) := i
end push
procedure pop ( i : int )
i := contents ( top )
top -= 1
end pop
end stack
The main program, which is in another file, gains access to the stack by importing it. Here is the main program:
import var stack % Use the stack
var n : int
…
stack . push ( n )
…
stack . pop ( n )
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| Details | In this example, the keyword var in the import list is required because the main program causes a change in the stack, by calling push and pop. The import lists of units that are modules, monitors and classes are used to gain access to further units. If the stack were in a file with a different name, say stk.t, the import list would be rewritten to use an in clause, as follows:
import var stack in "stk.t"A mainProgram is simply a program. See program.
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| See also | module, monitor and class. See also export list, import list, inherit list, implement list and implement by list.
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