Documentation for infix
eqv assembled from the following types:
sub infix:<eqv>(Any, Any)
Equivalence operator. Returns
True if the two arguments are structurally the same, i.e. from the same type and (recursively) contain equivalent values.
say [1, 2, 3] eqv [1, 2, 3]; # OUTPUT: «True␤»say Any eqv Any; # OUTPUT: «True␤»say 1 eqv 2; # OUTPUT: «False␤»say 1 eqv 1.0; # OUTPUT: «False␤»
Iterables cannot be compared, as they're assumed to be infinite. However, the operator will do its best and return
False if the two lazy
Iterables are of different types or if only one
Iterable is lazy.
say (1…∞) eqv (1…∞).List; # Both lazy, but different types; OUTPUT: «False␤»say (1…∞) eqv (1…3); # Same types, but only one is lazy; OUTPUT: «False␤»(try say (1…∞) eqv (1…∞)) # Both lazy and of the same type. Cannot compare; throws.orelse say $!.^name; # OUTPUT: «X::Cannot::Lazy␤»
eqv operator even works with arbitrary objects. E.g.,
eqv will consider two instances of the same object as being structurally equivalent:
mysay A.new(a => 5) eqv A.new(a => 5); # OUTPUT: «True␤»
Although the above example works as intended, the
eqv code might fall back to a slower code path in order to do its job. One way to avoid this is to implement an appropriate infix
mymulti infix:<eqv>(A , A )say A.new(a => 5) eqv A.new(a => 5); # OUTPUT: «True␤»
eqv does not work recursively on every kind of container type, e.g.
mysay Set(A.new(a => 5)) eqv Set(A.new(a => 5)); # OUTPUT: «False␤»
Even though the contents of the two sets are
eqv, the sets are not. The reason is that
eqv delegates the equality check to the
Set object which relies on element-wise
=== comparison. Turning the class
A into a value type by giving it a
WHICH method produces the expected behavior:
mysay Set(A.new(a => 5)) eqv Set(A.new(a => 5)); # OUTPUT: «True␤»
multi sub infix:<eqv>(ObjAt , ObjAt )
Returns True if the two ObjAt are the same, that is, if the object they identify is the same.
my = [2,3,1];my := ;say .WHICH eqv .WHICH; # OUTPUT: «True␤»