Why use this syntax?

Hello.

I'm quite new to programming in general, and I wonder if there is some logical reason to do the following.

When reading examples and descriptions of functions I often see:

    fileName = 'blabla.txt';
    newFile = fopen(fileName);

When I use fopen I type directly in the () instead of creating a variable holding the name, is there a good reason to do it as writen above?

Or is it simply good practice?

Answer 1

[Adam]

Personally I find it good practice to do the above, especially if the same thing is being used more than once. This is especially true of numbers or booleans where I don't like so-called "magic numbers" or "magic bools".

If you just call a function as:

myFunc( 7, true, 5, false );

it carries no meaning, whereas named variables do.

In your specific example this is not so much the case, but I still prefer to do this. It also makes it easier if, for example the filename is going to come from a UI or some other source where it would naturally be in a variable.

[David]

Hm, I will start doing that way. I'm sure I will benefit from it. Thanks

Answer 2

[Guillaume]

Most likely, the author plans to reuse filename later on in the code. For example:

filename = 'blabla.txt';
fid = fopen(filename, 'r');
if fid<1
   fprintf('Failed to open %s\n', filename);
else
   [a, count] = fread(fid, 2000, 'uint8');
   if count ~= 2000
      fprintf('%s was only %d bytes long\n', filename, count);
   end
end

It also allows you to refactor easily later. For example you may decide that filename comes from a function.

If it's only one time use, there's no advantage.