Documentation for method arity assembled from the following pages:

Class: Signature §

From Signature

(Signature) method arity §

method arity(Signature:D: --> Int:D)

Returns the minimal number of positional arguments required to satisfy the signature.

Class: ForeignCode §

From ForeignCode

(ForeignCode) method arity §

method arity()

Returns the arity of the enclosed code.

Class: Code §

From Code

(Code) method arity §

Defined as:

method arity(Code:D: --> Int:D)

Returns the minimum number of positional arguments that must be passed in order to call the code object. Any optional or slurpy parameters in the code object's Signature do not contribute, nor do named parameters.

sub argless() { }
sub args($a, $b?) { }
sub slurpy($a, $b, *@c) { }
say &argless.arity;             # OUTPUT: «0␤» 
say &args.arity;                # OUTPUT: «1␤» 
say &slurpy.arity;              # OUTPUT: «2␤»