Editing Raku (programming language) (section)

====Parameter passing modes====
Raku provides three basic modes of parameter passing: positional parameters, [[named parameter]]s, and slurpy parameters.

Positional parameters are the typical ordered list of parameters that most programming languages use. All parameters may also be passed by using their name in an unordered way. Named-only parameters (indicated by a <code>:</code> before the parameter name) can only be passed by specifying its name, i.e. it never captures a positional argument. Slurpy parameters (indicated by an <code>*</code> before the parameter name) are Raku's tool for creating [[variadic function]]s. A slurpy hash will capture remaining passed-by-name parameters, whereas a slurpy array will capture remaining passed-by-position parameters.

Here is an example of the use of all three parameter-passing modes:

<syntaxhighlight lang="raku">
sub somefunction($a, $b, :$c, :$d, *@e) {
    ...
}

somefunction(1, 2, :d(3), 4, 5, 6); # $a=1, $b=2, $d=3, @e=(4,5,6)
</syntaxhighlight>

Positional parameters, such as those used above, are always required unless followed by <code>?</code> to indicate that they are optional. Named parameters are optional by default, but may be marked as required by adding <code>!</code> after the variable name. Slurpy parameters are ''always'' optional.