is any SAS expression,
enclosed in parentheses. You must specify at least one expression.
Details
The expression is evaluated
at the bottom of the loop after the statements in the DO loop have
been executed. If the expression is true, the DO loop does not iterate
again.
Note: The DO loop always iterates
at least once.
Comparisons
There are three other
forms of the DO statement:
The DO statement, the simplest
form of DO-group processing, designates a group of statements to be
executed as a unit, usually as a part of IF-THEN/ELSE statements.
The iterative DO statement executes
statements between DO and END statements repetitively based on the
value of an index variable.
The DO WHILE statement executes
statements in a DO loop repetitively while a condition is true, checking
the condition before each iteration of the DO loop. The DO UNTIL statement
evaluates the condition at the bottom of the loop; the DO WHILE statement
evaluates the condition at the top of the loop.
Note: The statements in a DO UNTIL
loop always execute at least one time, whereas the statements in a
DO WHILE loop do not iterate even once if the condition is false.
Example: Using a DO UNTIL Statement to Repeat a Loop
These statements repeat
the loop until N is greater than or equal to 5. The expression N>=5
is evaluated at the bottom of the loop. There are five iterations
in all (0, 1, 2, 3, 4).