From type/independent-routines

See Original text in context

sub          squish( +values, |c)

Returns a sequence of values from the invocant/argument list where runs of one or more values are replaced with only the first instance. Like unique, squish uses the semantics of the === operator to decide whether two objects are the same. Unlike unique, this function only removes adjacent duplicates; identical values further apart are still kept. The order of the original list is preserved even as duplicates are removed.

Examples:

say <a a b b b c c>.squish; # OUTPUT: «(a b c)␤» 
say <a b b c c b a>.squish; # OUTPUT: «(a b c b a)␤»

The optional :as parameter, just like with unique, allows values to be temporarily transformed before comparison.

The optional :with parameter is used to set an appropriate comparison operator:

say [42, "42"].squish;                      # OUTPUT: «(42 42)␤» 
# Note that the second item in the result is still Str 
say [42, "42"].squish(with => &infix:<eq>); # OUTPUT: «(42)␤» 
# The resulting item is Int

From type/Supply

See Original text in context

method squish(Supply:D: :$as, :$with --> Supply:D)

Creates a supply that only provides unique values, as defined by the optional :as and :with parameters (same as with squish).

From type/Any

See Original text in context

multi method squish( :&as!, :&with = &[===] )
multi method squish( :&with = &[===] )

Similar to .repeated, returns the sequence of first elements of contiguous sequences of equal elements, after normalization by the function :as, if present, and using as an equality operator the :with argument or === by default.

"aabbccddaa".comb.squish.say;             # OUTPUT: «(a b c d a)␤» 
"aABbccdDaa".comb.squish( :as(&lc) ).say; # OUTPUT: «(a B c d a)␤» 
(3+2i,3+3i,4+0i).squish( as => *.re, with => &[==]).put; # OUTPUT: «3+2i 4+0i␤» 

As shown in the last example, a sequence can contain a single element. See squish for additional sub examples.