Switch Case with a range of letters?

OK, I'm just playing with some code. Here's the code:

clear, clc;
while 1

n = input('Type a Word Starting With a Capital Letter: ','s');
n=n(1);
switch n 
    case 'A'
        disp('An A word!')
        break;
    case 'B'
        disp('A B  word!')
        break;
    case 'C'
        disp('A C word!')
        break;
    case 'D' <= 'Z'
        disp("try using A,B or C this time") 
    otherwise 
        disp('incorrect word, I said use a CAPITAL!')
end
end

I added the "while true" to keep the program running until one of my cases is met. I'm trying to use a range from "D" to "Z" but it doesn't seem to work. I thought the characters were seen as an integer in programming so I'm not sure why it can't evaluate the case?

Answer 1

[Walter Roberson]

    case num2cell('D':'Z')

... Tested. It works.

[furcifer]

Thanks Walter.

Not to sound ungrateful, but do you know a way without num2cell function? I'm not sure if I can get awat with using Matlab's built in functions that we didn't explicitly cover. In another example we used were supposed to identify whether the input was lower or upper case. The "solution" uses if x >= 'A' && x<='Z' but I've run the code and it doesn't actually work! You need to use x>='F', which I can't figure out.

[Walter Roberson]

while 1
n = input('Type a Word Starting With a Capital Letter: ','s');
n=n(1);
switch true 
    case n == 'A'
        disp('An A word!')
        break;
    case n == 'B'
        disp('A B  word!')
        break;
    case n == 'C'
        disp('A C word!')
        break;
    case n >= 'D' && n <= 'Z'
        disp("try using A,B or C this time") 
    otherwise 
        disp('incorrect word, I said use a CAPITAL!')
end
end

[furcifer]

That seems to work. I'm not sure I understand the switch? "Frog" should fall under the 4th case either way shoudln't it? I'm not seeing something...

Answer 2

[Image Analyst]

Try this:

maxIterations = 20; % Whatever.  A failsafe
loopCounter = 1;
while loopCounter <= maxIterations
	n = input('Type a Word Starting With a Capital Letter: ','s');
	n = n(1); % Extract first letter only
	switch n
		case 'A'
			disp('An A word!')
			break;	% Quit look if they type an A word.
		case 'B'
			disp('A B  word!')
			break;	% Quit look if they type a B word.
		case 'C'
			disp('A C word!')
			break;	% Quit look if they type a C word.
		case {'D', 'E', 'F', 'G',      'Z'}  % Add all the others up to 'Z'
			uiwait(helpdlg("Try using A,B or C this time"))
		otherwise
			disp('Incorrect word, I said use a CAPITAL!')
	end
	loopCounter = loopCounter + 1;
end

[furcifer]

Thanks IA. I forgot how to use the curly brackets. The iterations loop was also helpful. I'm just writing some code trying to anticipate what might be asked. Any insights are appreciated.

Answer 3

[Steven Lord]

I made a couple modifications to your code.

foundCapitalLetter = false;

Rather than using while 1, I wanted to use something that immediately explains to anyone reading the code what's going on. At the start of the code, we haven't found a capital letter word yet so this variable starts off as false.

while ~foundCapitalLetter

If we enter or continue in the while loop, we haven't yet found a capital letter.

    str = input('Type a Word Starting With a Capital Letter: ','s');
    n = str(1);

I'm guessing you may want to do something with the word after the while loop so rather than throwing away all but the first letter I kept it around in a different variable.

    switch n 
        case 'A'
            disp('An A word!')
            foundCapitalLetter = true;

Success! We keep track of the fact that we succeeded by setting foundCapitalLetter to true. This will break us out of the while loop when we next get back to the top.

        case 'B'
            disp('A B  word!')
            foundCapitalLetter = true;
        case 'C'
            disp('A C word!')
            foundCapitalLetter = true;
        otherwise
            if ismember(n, 'D':'Z')

MATLAB knows how to make a sequence of letters using the colon operator. I don't know if you've learned the ismember function yet, but I think it's a more commonly used function than num2cell and so you may be okay using it. If not, you can use Walter's "n >= 'D' && n <= 'Z'" here.

                disp("try using A,B or C this time") 

We found a capital letter, but not one of the ones you'd accept, so foundCapitalLetter remains false.

            else
                disp('incorrect word, I said use a CAPITAL!')

No capital letter, try again. foundCapitalLetter remains false.

            end
    end
end