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Parameters and Arguments

This is (another) rant about misuse of technical terms.

Do you know what a parameter is?

How about an argument?

If you think they are the same, you aren't alone.

Consider this Kotlin code : 

class Test {
    fun foo( i : int ) = i + 1
    fun test() = foo(2)
}

What is i?

What is 2?

IMHO, the answers are :

  • i is a parameter of type Int.
  • 2 is an argument to the foo function.

Generic Types in Java

Edit

Now for a trickier example, involving generics : 

    interface List<E:Any> {
        fun get( index : Int ) : E
    }
    
    val myList = listOf<String>()

If we use reflection, then we can ask about E using : Class<List>.getTypeParameters() So far so good. So what does it return? An array of TypeVariables. WTF? They are NOT variables, they can't change. They don't even have a value!

The class TypeVariable should obviously be renamed TypeParameter.

They got the other half slightly wrong too :

List<String> is a ParameterizedType. The rawType is List, and the actualTypeArguments is an array size 1 containing String.

But why did they qualify it with the word actual? I suspect it's because they didn't realise it is redundant.

The word argument MEANS it is the actual type, just as 2 is the actual value (aka argument) passed to foo.

Grr.

Main

Edit

PS. Here's a classic main entry point for a Java application. 

    static int main( String... args ) { ... }

main has one parameter of type Array of Strings, and it is called args (short for arguments).

That's weird (calling a parameter arguments). ;-)) I'm not saying the name is wrong, just really odd! (I can't think of a good name).