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Comment by GuB-42 | Hacker News Reader

Sometimes, a number is just a number. The average of a, b, c is (a+b+c)/3, an positive interger is single digit when less then 10, the formula for the volume of a sphere is 4/3PIr^3, etc... And that's excluding 0, 1 and 2 which are naturally everywhere.

That some numbers are not magic would be obvious to a human reviewer, but the tool probably just treats any number in an expression as a magic number or something like that, and the workaround is to define constants for raw numbers. Which entirely defeats the purpose since now, people will just use these constants for actual magic numbers and the tool will see nothing.

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Maybe in rare cases, but in my experience, literals (numbers or strings) almost always have _some_ meaning where giving them a name helps readability. In my experience, it’s rare that “a number is just a number”. And sure, in those cases, naming them is silly.

Listen, what happens if we want to calculate delivery distances in a n-dimensional universe?

That 3 in your first example is definitely a magic number that should be either dynamically calculated from the number of elements being averaged, or defined as a const NUMBER_ELEMENTS_AVERAGED.

Sometimes a magic number is just a magic number.

If you name it `NUMBER_ELEMENTS_AVERAGED`, then when you add a new element to average, you will miss the fact that you also need to modify that value :)

You either have them on a list and calculate it dynamically based on the size, or have it as a magic number.

In the general case, of course you would use arrays (static or dynamic) and some kind of "size" attribute.

But this is just 3 values in an expression and using a constant could actually be bad. Let's be a bit more practical.

  int lightness(int r, int g, int b) { return (r+g+b)/3; }

Simple and straightforward

  int lightness(int r, int g, int b) {
    const int NUMBER_ELEMENTS_AVERAGED = 3;
    return (r+g+b)/NUMBER_ELEMENTS_AVERAGED; 
  }

Ok, I guess, but I think verbose for no good reason. But not as bad as the seemingly "cleaner"

  const int NUMBER_OF_COLOR_COMPONENTS = 3;
  int lightness(int r, int g, int b) {
    return (r+g+b)/NUMBER_OF_COLOR_COMPONENTS; 
  }

Imagine that you want want to add a color component, for example to support transparency (alpha). So you set NUMBER_OF_COLOR_COMPONENTS = 4, and then, your "lightness" function breaks, the simple (r+g+b)/3 would have stayed correct. That happened because didn't get the real meaning of that "3". Even if semantically, at the time you written that code, it is the number of color components, in reality, it is the number of terms in the expression. There is r, g, b: 3 terms, so 3. Who cares how many color components there are?

Side note: I know it is the wrong formula for lightness, that's just an example.

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