creating error_msg function

The issue I have is that:

You must write 4 functions. Three functions are for the area calculations: calc_circle_area, calc_rect_area, calc_triangle_are. These functions should do a calculation but NO input from the user. All user interaction must be done in the main script. The fourth function is called error_msg. Given an input string, it should display an appropriate message. For example
 >> error_msg(‘base’)
 value for base must be > 0
 no calculcation will be performed
 >> error_msg('length')
 value for length must be > 0
 no calculcation will be performed
 Hint: to concatenate two strings, enclose them in [ ]. For example,
 >> disp( ['Hello' 'world'])
 Helloworld

I have made the first three functions, I just am having problem creating the error_msg function. I don't understand how to do it, if anyone could help that would be great!

Answer 1

[Walter Roberson]

function error_msg(Name)
  phrase1 = 'value for ';
  phrase2 = ' must be > 0\nno calculation will be performed\n';
  phrase = char(zeros(1,length(phrase1)+length(Name)+length(phrase2));
  for K = 1 : length(phrase1)
    phrase(K) = phrase1(K);
  end
  for K = 1 : length(Name)
    phrase(length(phrase1)+K) = Name(K);
  end
  for K = 1 : length(phrase2)
    phrase(length(phrase1)+length(phrase2)+K) = phrase2(K);
  end
  fprintf(any(phrase),phrase);
end

[Fangjun Jiang]

What is your point, Walter?

[Walter Roberson]

Sorry, fixed the bug.

[Fangjun Jiang]

Walter, you probably don't have MATLAB to test it out. But I thought it could be done by:

fprintf('value for %s must be >0\nno calculation will be performed\n',Name);

[Fangjun Jiang]

Or use the hint that was suggested in the assignment.

disp(['value for ',Name,' must be >0']);

disp('no calculation will be performed');

[Walter Roberson]

The code form I used is very close to what would have to be used in a microprocessor in which string constants are compiled in to read-only memory.

[shanon]

Thank you both very much! The programming I am doing is very simple, so I used Fangjun's answer, but they both are great. Thanks for your time!

[Fangjun Jiang]

Walter, keep working on it. As of now, there are errors in the code. Passing that, fprintf() has run-time error.