Course of Raku / Essentials / More about types / Data type conversion / Exercises / True and False numbers

Solution: True and False numbers

The fastest way to explore the question is to throw a handful of candidate numbers at the ? operator at once and look at the results side by side:

for -2, -0.5, -1/3, 0, 1/3, 0.5, 2 -> $n {
    say "$n -> {?$n}";
}

The output makes the pattern obvious — every value prints True except the one in the middle:

-2 -> True
-0.5 -> True
-0.333333 -> True
0 -> False
0.333333 -> True
0.5 -> True
2 -> True

So the sign and the magnitude do not matter at all: only zero is falsy. The next question is whether that holds for every numeric type, because 0, 0.0, and 0e0 are an Int, a Rat, and a Num respectively:

my Int $int-zero = 0;
say ?$int-zero; # False

my Rat $rat-zero = 0.0;
say ?$rat-zero; # False

my Num $num-zero = 0e0;
say ?$num-zero; # False

Of course, nothing changes if you try to negate the number first:

my $int = 0;
say ?(-$int); # False

🦋 You can find the full program with the above example in the file true-false-numbers.raku.

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