Using single-character variable names for function parameters?

Question

Can using single-character variable names as parameters in a function okay?

For example, look at the code below:

public static int factorial (int x) {

    if (x == 0) {
        return 1;
    }

    return (x * factorial (x - 1));
}

In this case, is using variable name "x" okay as the parameter for the function? In which case would you want to avoid such thing?

Well, can you think a more meaningful name? Sure, call it variableOfWhichTheFactorialIsCalculatedAndReturned or variable_of_which_the_factorial_is_calculated_and_returned. — gnasher729, Aug 19 '16 at 22:48
If the method name leaves no room for interpretation of the meaning of the arguments, like for Add, it would it be fine to use a, b, c. Naming them first, second, third would add no meaning, you just want the sum of all. Another case could be for common formulas that everyone in the field knows like a^2 + b^2 = c^2 so a method named Hypothenuse or Diagonal on a Rectangle class could have arguments a and b and the code would return c but I would still document those in the header as "length of one side" and "length of the other side". — Martin Maat, Aug 20 '16 at 07:55
Is the variable used only in a small scope? Then a short name is good, — Brandin, Aug 21 '16 at 19:28

score 5 · Accepted Answer · edited Apr 12 '17 at 07:31

In your factorial example it's perfectly OK.

An example of how it would not be OK is:

public int calculateInterest(int x, int y, int z){
      //////
}

Because to calculate the interest you need to pass principal, rate and time.

Is the coder expected to pass them in that order asumming x is principal, y is rate and z is time?

I think not.

public int calculateInterest(int principal, int rate, int time){
      //////
}

In this answer from a similar question there's a list of acceptable cases for single-character or two-character variable names.

score 3 · Answer 2 · answered Aug 20 '16 at 01:11

Using meaningful name for function parameters is a way of making the code self-documented and you should do always do it.

Though, there are some situation where it can introduce unnecessary verbosity or even confusion. In these case it's ok to use a single letter. For example:

Purely arithmetic functions that takes a single number (usually x).
- OK: factorial(x), sin(x), etc.
- Unnecessary: abs(number)
When there exists conventional letters.
- OK: vectorLength(x0, y0, x1, y1), repeat(something, n).
- Obviously not OK: dotProduct(vector0horizontalComponent, vector0verticalComponent , vector1horizontalComponent, vector2verticalComponent),
- Unnecessarily verbose: repeat(something, numberOfRepetitions)
Trivial functions and small lambda expressions.
- OK: div(x,y) = x/y, map(u -> u.address.country, users)
- Unnecessarily verbose (but ok): , div(numerator, denominator), map(user -> user.address.country, users)
Highly generic code. Often seen in functional code, especially when using destructuring.
- OK: map(f, [x, xs]) = if xs == [] then [] else [f(x)] + map(f, xs)
- Unnecessarily verbose: map(functionToApply, [firstElementOfList, restOfList]) = ....

When readability inside a function is an issue, remember you can always use a variable to rename another locally, e.g:

function getRotationMatrix(angle) {
    var t = angle;
    return new Matrix([
        [+cos(t), -sin(t), 0],
        [+sin(t), +cos(t), 0],
        [0,       0,       1],
    ]);
}

The rule I follow is to keep names (whether for variables, parameters or even functions/methods/classes) as short as possible while still being perfectly clear within the context. Which means, among other things:

Longer names are useless if they don't contain useful information on the variable. E.g: userInstance, TextInput0, TextInput1
Longer names are useless if they contain redundant information : E.g. intYear, userList, UrlUtils.getUrlParser(...).parseUrl()
Avoid abbreviation as they are hardly ever totally unambiguous (except common ones in the language or domain)

TLDR: use names as long as necessary, no shorter, no longer.

Using single-character variable names for function parameters?

2 Answers2