While loops · Procedural

Build the idea

Start with the concept and its key vocabulary.

Key idea

Trace and write pre-test condition-controlled loops that terminate correctly.

A while loop checks its condition before every iteration. If the condition starts false, the body runs zero times. Use while when the number of repetitions is not known in advance, and make sure something inside the loop can eventually make the condition false.

Condition-controlled loop

A loop whose repetition is controlled by a Boolean condition.

while loop

A pre-test loop that repeats while its condition is true.

Pre-test

Checking a condition before executing the loop body.

Infinite loop

A loop that never reaches a false stopping condition.

Keep these in mind

ERL closes a while loop with endwhile.
Python uses a colon and indentation instead of an ending keyword.
The condition is checked before the first iteration.
A value used by the condition normally needs updating inside the body.

Build the idea

Start with the concept and its key vocabulary.

Key idea

Trace and write pre-test condition-controlled loops that terminate correctly.

Condition-controlled loop

A loop whose repetition is controlled by a Boolean condition.

while loop

A pre-test loop that repeats while its condition is true.

Pre-test

Checking a condition before executing the loop body.

Infinite loop

A loop that never reaches a false stopping condition.

Keep these in mind

ERL closes a while loop with endwhile.
Python uses a colon and indentation instead of an ending keyword.
The condition is checked before the first iteration.
A value used by the condition normally needs updating inside the body.