While loop execution with multiple numeric and logical conditions

I am unsure how to write a while loop that will run to check if an input is not within a specified domain and is also not numeric.

%ask for input

a = input('Select from list: ','s');

a = str2double(a);

while (a < 1 || a > 3 || ~(isfinite(a)) )

%display error message if input is invalid and ask for input again

fprintf('\nInput invalid\n')

a = input('Select from list: ','s');

a = str2double(a);

end

When I input a number greater than 1, the input passes the while loop and continues with the program.

Any help appreciated.

Answer 1

[Jan]

The code looks fine. Do you have a problem with it?

It is a good programming practice to avoid repeated code. Maybe this is "cleaner":

%ask for input
ready = false;
while ~ready
    a = input('Select from list: ');
    ready = (a >=1 && a <= 3);  % Then it must be finite also...
    if ~ready
       fprintf('\nInput invalid\n')
    end
end

Now you have one input command only. If you want to modify the text of the input command, you do not have to remember to change it at 2 locations.

If you use input() without the 's' flag, not-numerical inputs are avoided directly.

[Joseph Dal Bello]

Thanks for the answer!

I think I must have caused an error somewhere through the code repetition, your solution worked perfectly!