# an uncomprehensible "max"

hi! i dontunderstand the way this code runs :

```
ddom(x,y)=max(abs(x-0.5),abs(y-0.5))-0.5
catox(x,y)=abs(x-0.5)
catoy(x,y)=abs(y-0.5)
show(catox(10,20),";",catoy(10,20))
show(max(catox(10,20),catoy(10,20))-0.5)#19
show(max(catoy(10,20),catox(10,20))-0.5)#19
show("ddom=",ddom(10,20))#9???? <--- here
show("ddom=",ddom(20,10))#19
```

why 9 ???????????