how to use a while loop for switch case

I have this code:

transactionType= input('1:withdraw 2:deposit 3:account balance 4:end use');

switch transactionType

case 1

.....

case 2

.....

case 3

.....

case 4

.....

otherwise

disp ('invalid')

I need to make it so that, if a number other than 1, 2, 3, or 4 is entered, it displays this message, but also lets me enter a number again.

So is there a way to do that using a while loop.

Answer 1

[Walter Roberson]

try_again = true;
while try_again
  transactionType= input('1:withdraw 2:deposit 3:account balance 4:end use');
switch transactionType 
case 1
  if it works out
    try_again = false;
  end

So when you detect specifically that you are done then set the exit flag.

There is another way:

while true
transactionType= input('1:withdraw 2:deposit 3:account balance 4:end use');
switch transactionType 
case 1
  if everything works out
    break;
  end

do not break if you need to try again

Note that you would typically have an indefinite loop anyhow, to allow multiple transactions, continuing until the user ends (or a sanity check is reached)

[Jung woo Park]

thank U so much ❤

Answer 2

[Chunru]

repeat = true;
while repeat
    transactionType= input('1:withdraw 2:deposit 3:account balance 4:end use');
    repeat = false;         % this ensures exit if input is valid
    switch transactionType 
    case 1
        .....
    case 2
        .....
    case 3
        .....
    case 4
        .....
    otherwise
        disp ('invalid')
        repeat = true;      % repeat if invalid
    end
end