How to Get a script to end if a certain input is entered

I am new to MATLAB, and I have a general question about getting a script to end when an input is entered that does not fulfill the requirements. I know that it requires some sort of "for" statement, but i'm not sure how to inplement this.

I am currently working on a problem that I can use as an example:

Create a script that asks the user repeatedly for two time intervals in the form of hours, minutes, and seconds, and provides the addition of these two time intervals in the same form. The script should end if the input from the user is zero for all six values. You should write a function which takes in the given time intervals and returns their addition. The script will handle the user input, call the function, and display the corresponding output.

This is what I have so far:

clc
clear
flag = true;
while flag
    disp('Do you want to enter a time interval?')
    answer = input('Enter 1 for YES and 0 for NO :')
    if answer == 1
        hms1 = input("Enter the first time interval using 6 digits representing hours, minutes, and seconds: ");
        hms2 = input("Enter the second time interval using 6 digits representing hours, minutes, and seconds: ");
        intervalAddition(hms1, hms2);
        disp(hms1);
        disp(hms2);
    else
        flag = false;
    end
end

How do i get the script to end if the input is zero for all six values?

Answer 1

[Walter Roberson]

if hms1 == 0 || hms2 == 0
    flag = false;
else
        intervalAddition(hms1, hms2);
        disp(hms1);
        disp(hms2);
end

[Ashlee Rogers]

Thank you. I am assuming this is applicable in any situation?

[Walter Roberson]

No. That is applicable to the specific situation where you already have a termination flag set up.

The solution that is applicable to any situation is to set a termination flag and use break , and when you are within a nested loop, that the nesting loop should immediately test the termination flag and break if set -- and that should keep happening for every level of nested loop.

To clarify: break leaves only the inner-most level of nested loop. There are some computer languages where their break operation accepts an optional count of how many levels to exit, but MATLAB does not support that.

all_hms = zeros(1,10);
for K = 1 : 10
    still_going = true;
    while true
      hms1 = input( sprintf('Enter time interval #%d using 6 digits representing hours, minutes, and seconds: ', K));
      if hms1 == 0
          still_going = false;  %user wants to terminate outer loop
          break;
      end
      if ~isnumeric(x) || ~isscalar(x) || x < 0 | x >= 1e7
          disp('Enter a 6 digit positive integer');
      else
          break;  %we got what we need for the inner loop but we want to continue outer loop
      end
    end
    if ~still_going; break; end
    all_hms(K) = hms1;
end

Notice the termination flag is not set to false for the case of valid input being recognized, but that if the user enters invalid input then the code loops back to ask again within the same K value -- K is controlling number of full cycles of getting valid input, not the number of times we ask the user for input. This code is not "10 chances and you are out!" -- this code is "10 times, make as many mistakes as you want to enter a valid entry, but give up everything if 0 is entered."