Rookie needing some help with if-else and switch case.

I am a first year engineering student with no knowledge or background on programming. I have only been doing it for two weeks. I need some help with one of the programming assignments. I am only copying partial question because it is too long. I know I am somehow making mistake at the second switch statement but I am not sure what am I doing wrong. Any help or hint would be really appreciated. Thank You

clc
code = input ('Please enter a code to break: ','s');
digits = code - '0';

if length (digits) ~= 6;
    display ('Decoy Message: Not a six digit number')
else 
    if mod (sum (digits),2) == 1;
        display ('Decoy Message: Sum is odd')
    else
        day = (digits(1)*digits(2))-digits(3);
          switch day;
                case 1
                    day = 'Monday';
                case 2
                    day = 'Tuesday';
                case 3
                    day = 'Wednesday';
                case 4
                    day = 'Thursday';
                case 5
                    day = 'Friday';
                case 6
                    day = 'Saturday';
                case 7
                    day = 'Sunday';
              otherwise
                  display ('Decoy Message: Invalid rescue day')
          end
                  if 1 < day || day > 7;                      
                    if mod (digits(4),3)==0;
                       point = digits(5)-digits(6);
                    else point = digits(6)-digits(5);
                        switch point;
                                case 1
                                    point = 'bridge';
                                case 2
                                    point = 'library';
                                case 3
                                    point = 'river crossing';
                                case 4
                                    point = 'airport';
                                case 5
                                    point = 'bus terminal';
                                case 6
                                    point = 'hospital';
                                case 7
                                    point = 'St. Petes Church';
                            otherwise
                                display ('Decoy Message: Invalid rendezvous point')
                        end
                    end
                  end
    end
end

[Massimo Zanetti]

It works on my machine.. what is the problem?

[Harpreet Saini]

I have to run the following codes and I should only get 1 answer but my codes is not working the way it should

12345- Not a six digit number

208988 - sum is odd

397090 - invalid rescue day

918990 - invalid rendezvous point

132567- rescue on monday at the bridge

510129- rescue on friday at St. petes church

242350- rescue on saturday at the bus terminal

Answer 1

[Guillaume]

I suggest you learn how to debug your program. Had you stepped through you program you would have quickly found the issue.

Just from reading the code, it is clear to me that there is an issue with

                 if 1 < day || day > 7;                      
                    if mod (digits(4),3)==0;
                       point = digits(5)-digits(6);
                    else point = digits(6)-digits(5);
                        switch point;

As written, the switch point only happens when you're in the else part of the if ... else. So, when mod(..) == 0 you calculate point but never use it. I would think you're missing an end after the else.

By the way, you don't normally write a semicolon after an if or a switch.

Note that a much neater replacement to your switch statements is to use simple indexing. For example for the day, I would use:

daynames = {'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'};
day = (digits(1)*digits(2))-digits(3)
assert(mod(day, 1) == 0 && day >= 1 && day <= 7, 'Decoy Message: Invalid rescue day');  %make sure day is integer between 1 and 7
day = daynames{day};  %note that you're using the same variable name for the numeric and string day. Not good practice

[Harpreet Saini]

Thanks for the info, it gives me a hint on what I am doing wrong. As I said that I have only been using Matlab for 2 weeks and that too maybe for 12 hours in total. I dont think I can use the code that you have provided because we are not that far into the course.But your explanation 'switch' case only working in the 'else' part helpsa lot.

Again, I was not looking for an answer but just a hint and you helped me a lot. Thank you.