The do Statement
In this lesson, we introduce another statement to control a loop, the do statement.
We'll cover the following
Syntax
We have seen that the logic of a for
loop is identical to the logic of a while
loop. Both loops can end immediately after the first test of a given Boolean expression without executing the body of the loop. This behavior is desirable for most loops, so these two statements are the ones that we usually will use for our loops.
Occasionally, however, we will know in advance that the body of a loop must execute at least once. Although we could choose either a while
statement or a for
statement to implement such a loop, we could also use the do
statement. The do
statement executes its body, which includes the update step, before evaluating a Boolean expression to decide whether to continue the iteration.
The do
statement has the following form:
📝 Syntax: The
do
statementdo statement while (condition); <---- The semicolon is required
Effect: First, statement—which typically is a compound statement—executes. Next, the Boolean expression condition is evaluated. If it is true, statement executes again. Otherwise, the loop ends. The figure given below illustrates the logic of a
do
statement.
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