In Python, 7 // 2 is 3. In Raku, // means "or else, if there is no value", so 7 // 2 is 7.
In Python, // divides and drops the fraction. In Raku, // does not divide at all.
In Python
print(7 // 2)
print(7 % 2)
print(-7 // 2)3 1 -4
In Raku
say 7 // 2;
7
No error and no warning, only a wrong answer. That makes this the more dangerous kind of false friend.
Why
In Raku, // is the defined-or operator. It gives you the left side if the left side has a value, and the right side if it does not. 7 has a value, so the answer is 7, and the 2 is never looked at.
Its job is giving defaults:
my $nickname; say $nickname // 'no nickname'; my $city = 'Turin'; say $city // 'unknown';
no nickname Turin
$nickname was declared but never given a value, so // uses the text on the right. $city has a value, so // keeps it.
If you come from Perl, this is nothing new: Perl’s // means the same.
my $nickname;
print $nickname // "no nickname", "\n";no nickname
Say it in Raku
Integer division is div, and the remainder is %:
say 7 div 2; say 7 % 2; say 7 / 2;
3 1 3.5
/ is ordinary division and keeps the fraction: 3.5.
With negative numbers, div rounds down, the same way Python’s // does:
say -7 div 2; say -7 % 2;
-4 1