shell script : condition without if

[will@localhost ShellScript]$ cat cond.sh
#!/bin/sh

read -p "Please input (Y/N): " yn

[ "$yn" == "Y" -o "$yn" == "y" ] && echo "Oh, Yes!" && exit 0
[ "$yn" == "N" -o "$yn" == "n" ] && echo "Oh, No!" && exit 0
echo "I don't know what your choice is." && exit 0
[will@localhost ShellScript]$