About While Loops problems

Is there anyway to end the program by entering "quit"? As the program keeps going despite displays "Exiting..."

The following is the syntax.

function Individual_Project_Final()

disp('Welcome to Unit Converter interface! ');

disp(' ');

while true

% Accept user input

input_str = input('Enter a number to be converted (or type "quit" to exit program): ', 's');

% Check if the user wants to quit

if strcmp(input_str, 'quit')

disp('Exiting...')

break;

end

% Convert input string to a number

numin = str2double(input_str);

% Check if the input is a valid number

if isnan(numin)

disp('Input invalid. Please enter a whole or decimal number (or type "quit to exit program): ');

else

disp('Input valid. Now please select the unit conversion type (or type "quit to exit program): ');

break;

end

end

% Display the menu for selecting conversion type

disp(' ')

disp('Select conversion type:')

disp('1) Celsius to Fahrenheit')

disp('2) Fahrenheit to Celsius')

disp('3) Centimeters to Inches')

disp('4) Inches to Centimeters')

disp('5) Meters to Foot')

disp('6) Foot to Meters')

disp('7) Kilometers to Miles')

disp('8) Miles to Kilometers')

disp('9) Grams to Ounces')

disp('10) Ounces to Grams')

disp('11) Kilograms to Pounds')

disp('12) Pounds to Kilograms')

disp('13) Tonnes to Tons')

disp('14) Tons to Tonnes')

while true

% Accept user input

input_str = input('Please select conversion type (1-14) (or type "quit" to exit): ', 's');

% Check if the user wants to quit

if strcmp(input_str, 'quit')

disp('Exiting...');

break;

end

% Convert input string to a number

convtype = str2double(input_str);

% Check if input is a valid conversion type

if ~ismember(convtype, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14])

disp('Conversion type invalid. Please enter a number from 1 to 14 (or type "quit to exit program): ');

else

disp('Input valid. We are now finalizing the resluts based on your input. ');

break;

end

end

% Call the user-defined function from Module 2

[numout,unit] = MyUnitConverter(numin,convtype);

% Output generation

disp(' ');

fprintf('The converted number is: %.2f %s\n', numout, unit);

end

[VBBV]

If you want to quit entire program, type quit again in command window

[Stephen23]

I suspect that you want RETURN rather than QUIT or BREAK.

[VBBV]

@Stephen23 yes, return would be more suitable than quit or break

Answer 1

[VBBV]

It has already exited, the first while loop, but it's waiting for next input from user ... See the message at bottom left of window in workspace, you need to select or provide a number

[VBBV]

E.g. Enter 1 or 2 in command window

[CHUN HIN KYLE]

How can I stop the program from moving on once the user enter "quit"?

[CHUN HIN KYLE]

Can I make it to exit entirely just by entering "quit" once?

[VBBV]

@CHUN HIN KYLE you need to put the end keyword at the end of function i.e. one line ahead of function end (see below) . Since there are multiple while loops inside your function, the program instructions (if any) still get executed after exiting the first while loop. So to exit the program using only one quit, putting the end keyword at the end will force the break statement to exit the entire while loop.

>> Individual_Project_Final  % call the function from command window 

function Individual_Project_Final() 
disp('Welcome to Unit Converter interface! '); 
disp(' '); 
while true
    % Accept user input
    input_str = input('Enter a number to be converted (or type "quit" to exit program): ', 's'); 
    
    % Check if the user wants to quit 
    if strcmp(input_str, 'quit') 
        disp('Exiting...')
        break; 
    end 
    % Convert input string to a number 
    numin = str2double(input_str); 
    % Check if the input is a valid number 
    if isnan(numin) 
        disp('Input invalid. Please enter a whole or decimal number (or type "quit to exit program): '); 
     
    else 
        disp('Input valid. Now please select the unit conversion type (or type "quit to exit program): '); 
        break; 
    end 

    
    % Display the menu for selecting conversion type
    disp(' ')
    disp('Select conversion type:')
    disp('1) Celsius to Fahrenheit')
    disp('2) Fahrenheit to Celsius')
    disp('3) Centimeters to Inches')
    disp('4) Inches to Centimeters')
    disp('5) Meters to Foot')
    disp('6) Foot to Meters')
    disp('7) Kilometers to Miles')
    disp('8) Miles to Kilometers')
    disp('9) Grams to Ounces')
    disp('10) Ounces to Grams')
    disp('11) Kilograms to Pounds')
    disp('12) Pounds to Kilograms')
    disp('13) Tonnes to Tons')
    disp('14) Tons to Tonnes')
        while true 
            % Accept user input
            input_str = input('Please select conversion type (1-14) (or type "quit" to exit): ', 's'); 
            
            % Check if the user wants to quit
            if strcmp(input_str, 'quit')
                disp('Exiting...'); 
                break;
            end 
            % Convert input string to a number 
            convtype = str2double(input_str); 
            % Check if input is a valid conversion type 
            if ~ismember(convtype, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]) 
                disp('Conversion type invalid. Please enter a number from 1 to 14 (or type "quit to exit program): '); 
            else 
                disp('Input valid. We are now finalizing the resluts based on your input. '); 
                break; 
            end 
        end 

%
    % Call the user-defined function from Module 2 
    [numout,unit] = MyUnitConverter(numin,convtype); 
    % Output generation 
    disp(' '); 
    fprintf('The converted number is: %.2f %s\n', numout, unit); 

%>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
end % put the end of the first while before the end of function  
end 

[CHUN HIN KYLE]

Thanks, it worked!

Also, how am I gonna keep this program going in this case?

[VBBV]

@CHUN HIN KYLE, if the user wants to continue further, you can modify the program as shown below

>> Individual_Project_Final  % call the function from command window 

function Individual_Project_Final() 
disp('Welcome to Unit Converter interface! '); 
disp(' '); 
while true
    % Accept user input
    input_str = input('Enter a number to be converted (or type "quit" to exit program): ', 's'); 
    
    % Check if the user wants to quit 
    if strcmp(input_str, 'quit') 
        disp('Exiting...')
        break; 
    end 
    % Convert input string to a number 
    numin = str2double(input_str); 
    % Check if the input is a valid number 
    if isnan(numin) 
        disp('Input invalid. Please enter a whole or decimal number (or type "quit to exit program): '); 
     
    else 
        disp('Input valid. Now please select the unit conversion type (or type "quit to exit program): '); 
       % break; This break statement will stop program even when input is
       % valid
    end 

    
    % Display the menu for selecting conversion type
    disp(' ')
    disp('Select conversion type:')
    disp('1) Celsius to Fahrenheit')
    disp('2) Fahrenheit to Celsius')
    disp('3) Centimeters to Inches')
    disp('4) Inches to Centimeters')
    disp('5) Meters to Foot')
    disp('6) Foot to Meters')
    disp('7) Kilometers to Miles')
    disp('8) Miles to Kilometers')
    disp('9) Grams to Ounces')
    disp('10) Ounces to Grams')
    disp('11) Kilograms to Pounds')
    disp('12) Pounds to Kilograms')
    disp('13) Tonnes to Tons')
    disp('14) Tons to Tonnes')
        %while true 
            % Accept user input
           % input_str = input('Please select conversion type (1-14) (or type "quit" to exit): ', 's'); 
            
            % Check if the user wants to quit
            %if strcmp(input_str, 'quit')
               % disp('Exiting...'); 
              %  break;
           % end 
            % Convert input string to a number 
            convtype = str2double(input_str); 
            % Check if input is a valid conversion type 
            if ~ismember(convtype, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]) 
                disp('Conversion type invalid. Please enter a number from 1 to 14 (or type "quit to exit program): '); 
            else 
                disp('Input valid. We are now finalizing the resluts based on your input. '); 
                %break; 
            end 
       % end 
% Call the user-defined function from Module 2 
%>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
% The user defined function also has a display list of unit conversion
% categories as mentioned in my answer to one of your previous questions
% Its best to avoid redundant display of user query  options both inside the
% my unit converter program as well as in this program. You can take choice
% which one to delete the redundant display of user query options.
%>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

[numout,unit] = MyUnitConverter(numin,convtype); 
% Output generation 
disp(' '); 
fprintf('The converted number is: %.2f %s\n', numout, unit); 
% add a line of code which asks user to continue further
    c = input('Do you want to continue further ?:Type "Yes" (or type quit to exit):','s')
    if strcmp(c,'Yes')
        disp(' ')                    
    elseif strcmp(c,'quit')
        break; 
    end
%>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
end % put the end of the first while before the end of function  
end 

[VBBV]

You could try using continue statement in the else part of code when the user enters inputs that are valid.

[CHUN HIN KYLE]

Sorry, the loop just repeated itself instead of moving down after replacing "break" with "continue" after else part of code when the user enters inputs that are valid.

[VBBV]

Try using the code which i modified (that has only one while loop , inner while loop is commented )