rhai/doc/src/language/overload.md

Function Overloading

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[Functions] defined in script can be overloaded by arity (i.e. they are resolved purely upon the function's name and number of parameters, but not parameter types since all parameters are the same type - [Dynamic]).

New definitions overwrite previous definitions of the same name and number of parameters.

fn foo(x,y,z) { print("Three!!! " + x + "," + y + "," + z); }

fn foo(x)     { print("One! " + x); }

fn foo(x,y)   { print("Two! " + x + "," + y); }

fn foo()      { print("None."); }

fn foo(x)     { print("HA! NEW ONE! " + x); }   // overwrites previous definition

foo(1,2,3);     // prints "Three!!! 1,2,3"

foo(42);        // prints "HA! NEW ONE! 42"

foo(1,2);       // prints "Two!! 1,2"

foo();          // prints "None."