How to loop through arguments in Bash ($1 $2 $3 and so forth)?

I have the following code snippet

for num
do
   echo $num
done

But I don't understand why it works! How come does Bash know to loop through my params $1, $2, $3, $... using my personal taste of "num" variable???

It's a feature of bash:

for num; do ...

is a shorthand for

for num in "$@"; do ...

The documentation is at http://www.gnu.org/software/bash/manual/bashref.html#Looping-Constructs

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