In role Rational§

See primary documentation in context for method isNaN

method isNaN(Rational:D: --> Bool:D)

Tests whether the invocant's Num value is a NaN, an acronym for Not available Number. That is both its numerator and denominator are zero.

In Complex§

See primary documentation in context for method isNaN

method isNaN(Complex:D: --> Bool:D)

Returns true if the real or imaginary part is NaN (not a number).

say (NaN+5i).isNaN# OUTPUT: «True␤» 
say (7+5i).isNaN;   # OUTPUT: «False␤»