Why sort half-blood Riddle into Slytherin?

[karen at dacafe.com]

No: HPFGUIDX 108538

Hi all,
This question may have been answered but with the sorting hat's song in
OOP I want to know how Tom Riddle with his half-blood hertitage got sorted
into Slytherin?

Could there be other "half-bloods" in Slytherin?

Thanks for the chance to ask this question,

kmc