do statement - xtclang/xvm GitHub Wiki

The do statement is very similar to the while statement, except that it always executes its body (the statement block) at least one time.

Execution of the do statement begins with the execution of the body. After the execution of the body, the do statement evaluates the ConditionList, which controls whether the loop will be repeated. If the ConditionList evaluates to True, then the do statement executes from the beginning (it loops); otherwise, if the ConditionList evaluates to False or short-circuits, then the do statement completes.

Execution of a break statement that applies to the do statement causes the do statement to complete.

Execution of a continue statement that applies to the do statement causes the do statement to advance its execution to the ConditionList.

Like the while statement, a do statement labeled by a LabeledStatement provides two read-only label variables that expose the state of the loop:

Name	Type	Description
first	Boolean	True iff this is the first iteration of the loop
count	Int	The count of completed iterations of the loop

The statement block is reachable if the do statement is reachable. The ConditionList is reachable if the statement block completes, or if a continue statement that applies to the do statement is reachable; the ConditionList completes if it is reachable and completes or short-circuits. The do statement completes if the ConditionList completes and is not the constant True, or if a break statement that applies to the do statement is reachable.

Definite assignment rules:

• The VAS before the statement block is the VAS before the do statement.
• The VAS before the ConditionList is the VAS after the statement block.
• The VAS after the do statement is the VAS after the ConditionList.

The do statement provides a local variable scope that includes both the statement block and the ConditionList; this scope is used by the statement block in lieu of its own local variable scope, such that variables declared within the statement block are still in scope when the ConditionList executes. This unusual arrangement allows the loop’s ConditionList to reference information otherwise available only within the statement block.

    DoStatement:
        do StatementBlock while ( ConditionList )

From IfStatement:

    ConditionList:
        Condition
        ConditionList , Condition

    Condition:
        Expression
        OptionalDeclaration ConditionalAssignmentOp Expression
        ( OptionalDeclarationList , OptionalDeclaration ) ConditionalAssignmentOp Expression

    ConditionalAssignmentOp:
        :=
        ?=

And from VariableStatement:

    OptionalDeclarationList:
        OptionalDeclaration
        OptionalDeclarationList , OptionalDeclaration

    OptionalDeclaration:
        Assignable
        VariableTypeExpression Name

    VariableTypeExpression:
        val
        var
        TypeExpression

    Assignable:
        Name
        TernaryExpression . Name
        TernaryExpression ArrayIndexes