How to find length of user input?

Hi everyone. I have a program here to determine ISBN numbers of a given 9 digit number. However, I am running into some difficulty.

clc
clear

isbn = input('Enter a nine digit ISBN number:' );

if length(isbn) == 9   
    
    d1 = str2num(isbn(1));
    d2 = str2num(isbn(2));
    d3 = str2num(isbn(3));
    d4 = str2num(isbn(4));
    d5 = str2num(isbn(5));
    d6 = str2num(isbn(6));
    d7 = str2num(isbn(7));
    d8 = str2num(isbn(8));
    d9 = str2num(isbn(9));
    
    A = (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9);
    mod (A, 11);
    d10 = mod;
    
    if d10 ~= 10
        fprintf ("ISBN-10: %f-%f%f-%f%f%f%f%f%f-%f",d1, d2, d3, d4, d5, d6, d7, d8, d9, d10);
    elseif d10 == 10
        d10 = X;
        fprintf ("ISBN-10: %f-%f%f-%f%f%f%f%f%f-%f",d1, d2, d3, d4, d5, d6, d7, d8, d9, X); 
        
    end
else if length(isbn) ~= 9
        disp ('Error, ISBN must be exactly 9 digits.')
    end
end

I am trying to get the length of the user input, but everytime I type in a 9 digit number, it reads me the Error display I wrote. It is not realizing the length value of "123456789" as 9 but rather as 1. Any suggestions?

Answer 1

[Stephan]

Hi,

a lots of bugs in this - i think i fixed them all:

clc
clear
isbn = input('Enter a nine digit ISBN number:' );
isbn = char(string(isbn));

if strlength(string(isbn)) == 9   
    d1 = str2double(isbn(1));
    d2 = str2double(isbn(2));
    d3 = str2double(isbn(3));
    d4 = str2double(isbn(4));
    d5 = str2double(isbn(5));
    d6 = str2double(isbn(6));
    d7 = str2double(isbn(7));
    d8 = str2double(isbn(8));
    d9 = str2double(isbn(9));
    A = (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9);
    d10 = mod (A, 11);
    
    if d10 ~= 10
        fprintf ("ISBN-10: %d-%d%d-%d%d%d%d%d%d-%d\n",d1, d2, d3, d4, d5, d6, d7, d8, d9, d10);
    elseif d10 == 10
        d10 = 'X';
        fprintf ("ISBN-10: %d-%d%d-%d%d%d%d%d%d-%s\n",d1, d2, d3, d4, d5, d6, d7, d8, d9, d10); 
    end
    
else
    if length(isbn) ~= 9
        disp ('Error, ISBN must be exactly 9 digits.')
    end
end

Best regards

Stephan

[Ashwin Sivalingam]

Thank you very much Stephan, this works. However, when entering in a value that begins with 0, for ex, 012345678, it ignores the 0 and counts 8 digits. Any fix?

[Stephan]

clc
clear
isbn = input('Enter a nine digit ISBN number:', 's');
if strlength(isbn) == 9   
    d1 = str2double(isbn(1));
    d2 = str2double(isbn(2));
    d3 = str2double(isbn(3));
    d4 = str2double(isbn(4));
    d5 = str2double(isbn(5));
    d6 = str2double(isbn(6));
    d7 = str2double(isbn(7));
    d8 = str2double(isbn(8));
    d9 = str2double(isbn(9));
    A = (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9);
    d10 = mod (A, 11);
    
    if d10 ~= 10
        fprintf ("ISBN-10: %d-%d%d-%d%d%d%d%d%d-%d\n",d1, d2, d3, d4, d5, d6, d7, d8, d9, d10);
    elseif d10 == 10
        d10 = 'X';
        fprintf ("ISBN-10: %d-%d%d-%d%d%d%d%d%d-%s\n",d1, d2, d3, d4, d5, d6, d7, d8, d9, d10); 
    end
    
else
    if length(isbn) ~= 9
        disp ('Error, ISBN must be exactly 9 digits.')
    end
end

should work

Answer 2

[emad xa]

i run program have a problem

Undefined function or variable 'strlength'.

Error in Q3 (line 4)

if strlength(isbn) == 9