Subset UInt
Unsigned integer (arbitrary-precision)
The UInt is defined as a subset of Int:
my subset UInt of Int where {not .defined or $_ >= 0};
Consequently, it cannot be instantiated or subclassed; however, that shouldn't affect most normal uses.
Some examples of its behavior and uses:
say UInt ~~ Int; # OUTPUT: «Trueâ€Â»
my UInt $u = 0xffff_ffff_ffff_ffff_ffff_ffff_ffff_ffff; # 64-bit unsigned value
say $u.base(16); # OUTPUT: «FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFâ€Â» (32 digits)
++$u;
say $u.base(16); # OUTPUT: «100000000000000000000000000000000â€Â» (33 digits!)
my Int $i = $u;
say $i.base(16); # same as above
say $u.^name; # OUTPUT: «Intâ€Â» - UInt is a subset, so the type is still Int.
say $i.^name; # OUTPUT: «Intâ€Â»
# Difference in assignment
my UInt $a = 5; # nothing wrong
my UInt $b = -5; # Exception about failed type check
my UInt $c = 0;
--$c; # Exception again
CATCH { default { put .^name, ': ', .Str } };
# OUTPUT: «X::TypeCheck::Assignment: Type check failed in assignment to $b; expected UInt but got Int (-5)â€Â»
# Non-assignment operations are fine
my UInt $d = 0;
say $d - 3; # OUTPUT: «-3â€Â»