Perl Tutorial - 33: Redo Statement Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming

hello guys welcome to my channel this is
the 33rd tutorial in this course and in
this year old we'll be talking about the
redo statement and pearl so before I
talk to you about what the redo
statement is used for I want you to take
a look at the code that I have written
in this script riru dot PL and on line
number three I have heared a scalar
variable a that has a value of ten and
then I have a while loop on line number
five with the test condition a less than
twenty so you know ideally this loop
should have how many iterations ten
iterations because we are incrementing
the value of a by one in each iteration
I have an update statement on line
number eight and before this I have a
print statement on line number seven
which is first going to display the text
of value of a is and then it's going to
display the current value of a and you
could just ignore the if block that I
have on line number nine you know the
statement has a test condition a equals
20 but I don't have any executable code
inside the safe block because I have a
reduced rating but I have commented out
so essentially this if statement amounts
nothing for the time being and you know
you could just assume that this this
while loop has only two executable
statements so I'll make sure this file
save and I'll show you the output of
this script before talking about the
redo statement so we see a value of a is
10 11 12 13 14 15 16 17 18 and 19 we
don't see the value 20 because the test
condition here in the while loop is
while a is less than 20 and not while a
is less than or equal to 20 now let's
say you want to you know have another
iteration for the while loop for the
value 20 even though the test condition
here states otherwise you could do that
using the reduce statement and all I do
with the script is remove the hash
characters to uncomment this redo
statement and now you know let's say the
value of a is 19 we are going to print
the value of a is 19 then we are going
to change the value of a to 20 and
earlier that would have been the last
statement that the script would have
executed because as soon as a would have
gotten to 20 this past condition would
have failed and the loop won't have had
any more iterations but now we're going
to get to this if statement where we
check a is a 20 and this would evaluate
to true we would have gotten inside the
if block and this redo statement would
have executed and the reduced rate wind
basically forces another iteration of
the loop irrespective of whether the
test condition is true or false so you
know this is not like do-while don't
confuse redo but do while this is still
the regular while loop it's just that we
are forcing a nitration using redo right
so when this would work the test
condition will not be evaluated we would
get to the print statement straight away
and we would print the value of a is 20
and then we would update a and then you
know everything would work normally we
would not have any more I trations
because they would then become 21 this
if statement will not evaluate to true
and you know this would obviously fail
and everything is going to be over so
and make sure the file saved I'll press
f5 to run and now we see an additional
line of output we see that the value of
a is 20 is also displayed and this could
be attributed solely to the reduced
statement that we have here in the
script on line number 11 so I hope this
is clear and you may subscribe to my
channel if you haven't already and if
you have any doubts regarding the
reduced statement if I haven't done a
good job of explaining it then you know
you could obviously write comments to on
the video and I would try to
reply as soon as possible and elaborate
in other ways if I can