Documentation for method assuming

Documentation for method assuming, assembled from the following types:

role Callable

From Callable

(Callable) method assuming

method assuming(Callable:D $self: |primers)

Returns a Callable that implements the same behaviour as the original, but has the values passed to .assuming already bound to the corresponding parameters.

my sub slow($n){ my $i = 0$i++ while $i < $n$i };
# takes only one parameter and as such wont forward $n 
sub bench(&c){ cnow - ENTER now };
say &slow.assuming(10000000).&bench# OUTPUT: «(10000000 7.5508834)␤» 

For a sub with arity greater than one, you can use Whatever * for all of the positional parameters that are not "assumed".

sub first-and-last ( $first$last ) {
    say "Name is $first $last";
my &surname-smith = &first-and-last.assuming*'Smith' );
&surname-smith.'Joe' ); # OUTPUT: «Name is Joe Smith␤» 

You can handle any combination of assumed and not assumed positional parameters:

sub longer-names ( $first$middle$last$suffix ) {
    say "Name is $first $middle $last $suffix";
my &surname-public = &longer-names.assuming**'Public'* );
&surname-public.'Joe''Q.''Jr.'); # OUTPUT: «Name is Joe Q. Public Jr.␤» 

Named parameters can be assumed as well:

sub foo { say "$^a $^b $:foo $:bar" }
&foo.assuming(13:42foo)(24:72bar); # OUTPUT: «13 24 42 72␤» 

And you can use .assuming on all types of Callables, including Methods and Blocks:

# We use a Whatever star for the invocant: 
my &comber = Str.^lookup('comb').assuming: *, /\w+/;
say comber 'Perl is awesome! Python is great! And PHP is OK too';
# OUTPUT: «(Perl Python PHP)␤» 
my &learner = {
    "It took me $:months months to learn $^lang"
}.assuming: 'Perl 6';
say learner :6months;  # OUTPUT: «It took me 6 months to learn Perl 6␤»