▶ BREAK STATEMENT
Break statements are used when the execution of looping statement needs to be stopped
immediately.
To make a break statement, write:
To make a break statement, write:
%
Tyl symbolizer will replace the percent code: '%', with: '✖', the break symbol:
✖
Break statement must be written in its own line (except for one-line statements)!
Say we have a list of numbers, and we want to find the index of the first number that is less than or equal to 3:
Say we have a list of numbers, and we want to find the index of the first number that is less than or equal to 3:
nums 5 6 1 0
matched_index -1
index 4 ~
num nums index
num <= 3 ?
matched_index index
✖
ᐤ
ᐤ
print matched_index
2
matched_index starts with: -1. In the looping, when the current item of
nums satisfies the condition: 'num <= 3', matched_index gets the current
index. The break line: '✖', will cause the looping to terminate, and the program
will continue right after the looping, in the line: 'print matched_index',
where it will print: 2.Note that even though the break statement is in the repeat block of a conditional statement, it causes the system to search up the statements tree and find the first enclosing looping statement. If found, it will cause that looping to terminate.
In Variable Assignment - Part 4, there is a pseudo-code in
get_last_messages function.Let's try and implement it:
main »
messages 'message #7080' 'message #7081' 'message #7082' 'message #7083' 'message #7084'
get_last_messages messages 3 last_messages
print last_messages
get_last_messages messages num last_messages »
message_ind len messages
messages_ctr num
on ~
message_ind --
messages_ctr --
messages_ctr < 0 ? ✖
message messages message_ind
last_messages message
ᐤ
[ 'message #7084', 'message #7083', 'message #7082' ]
In
In line: '
Up to now, it's all fine. But what happens when there are less than three messages in
When
The solution is:
get_last_messages function, message_ind tracks the messages
downward, each time adding the current message to last_messages parameter.
messages_ctr acts as the stop counter, to stop the
conditional
looping
after num times, thus last_messages will have
the appropriate messages.In line: '
messages_ctr < 0 ? ✖', when
messages_ctr goes below zero, it activates the break statement: '✖',
and the program continues after the looping (effectively, out of the function).Up to now, it's all fine. But what happens when there are less than three messages in
messages list?When
messages_ctr will be zero, and still in the valid stop counting range,
message_ind will be: -1, and the get current message line:
'message messages message_ind', will be invalid since message_ind
is out-of-range!The solution is:
main »
messages 'message #7080' 'message #7081'
get_last_messages messages 3 last_messages
print last_messages
get_last_messages messages num last_messages »
message_ind len messages
messages_ctr num
on ~
message_ind --
messages_ctr --
message_ind < 0 ? ✖
messages_ctr < 0 ? ✖
message messages message_ind
last_messages message
ᐤ
[ 'message #7080', 'message #7081' ]
As it becomes apparent,
Usually break statement is placed inside a conditional statement . But there are some times where it can be used also arbitrarily.
For ex., while debugging:
message_ind, can act also as a stop counter for
such case, and the stop line: 'message_ind < 0 ? ✖', is
added.Usually break statement is placed inside a conditional statement . But there are some times where it can be used also arbitrarily.
For ex., while debugging:
num 0
on ~
num ++
print num
✖
ᐤ
1
The looping is breaked after one iteration, to see if the repeat block is working
correctly.