import std.stdio;

void main()
{
    pure bool leapYear(uint y)
    {
        auto result = (y % 4) == 0 && (y % 100 || (y % 400) == 0);
        if (result) writeln(y, " is a leap year!"); // Error!
        // Cannot call impure function writeln from pure function!
        return result;
    }

    leapYear(1);
}