Put default arguments on function declaration

Default parameter values arguably are better suited on the declaration since that is the only thing that a caller always sees.

You can have the argument on the definition as well but if you put it on the definition then only those who see the definition would be able to use the default value (https://stackoverflow.com/questions/1142209/what-if-the-default-parameter-value-is-defined-in-code-not-visible-at-the-call-s).

🚩 You can not have default values on both declaration and definition. I don’t know why this is the case. My guess is that if default values are different in one place then they will be issues.

Following is a good idea.

// Declaration
void foo(int x = 3.14, const char* y = "pi");

// Definition.
void foo(int x /*= 3.14 */, const char* y /*= "pi" */)
{
   ...
}