The while instruction constructs a loop subject to a terminating condition.
Syntax
The syntax of the while instruction is:
while condition do [:label]
[while-instructions]
endwhile [label];
Description
The condition is an expression that must produce a value of type
While the condition remains true, the optional while-instructions are executed following the evaluation of the condition. The loop terminates when the value of the condition is evaluated as false.
If the condition is initially false, the optional while-instructions are not executed. (For details about evaluating a condition once at the start of a loop, see "Iterating over a Range of Numeric Values", under "foreach Instruction", later in this chapter.)
You can nest while instructions within each other to any level. The break instruction can be used to terminate a while loop prematurely or the continue instruction can be used to cause the next iteration of a while loop to begin.
The optional :label identifier is used to nominate the specific loop (within a group of nested loops) that may be terminated or continued by a break or continue instruction, respectively. When the break or continue instruction is used without a label, only the innermost loop is terminated or continued. For more details, see "break Instruction" or "continue Instruction", later in this chapter.
Example
The following example shows the use of the while instruction.
writeCustomers(customerArray: CustomerArray);
vars
count : Integer;
cust : Customer;
begin
count := 1;
while count <= customerArray.size do
cust := customerArray[count];
write "Customer " & count.String & ":" & cust.name;
count := count + 1;
endwhile;
end;