Course of Raku / Essentials / Data type conversion

Introspection with WHAT

It is possible to see the type of data in a variable by calling the WHAT method on it:

my $n = 42;
my $s = '42';
say $n.WHAT; # (Int)
say $s.WHAT; # (Str)

The type is printed in parentheses, as shown in the comments. For example, (Int) or (Str).

There is no problem to call a method on a literal itself. For example:

say 42.WHAT;      # (Int)
say (-1).WHAT;    # (Int)
say 'Hello'.WHAT; # (Str)
say True.WHAT;    # (Bool)

Notice that in the case of -1, we put the number in parentheses, as say -1.WHAT would try to negate the result of 1.WHAT, which leads to an exception.


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