How is 0xe foo parsed?

I know that it is parsed as a whole preprocessing number, but i dont get why, because, how can the operator " " be a pp-number?

pp-number : 
digit
. digit
pp-number digit
pp-number identifier-nondigit 
pp-number ’ digit 
pp-number ’ nondigit 
pp-number e sign
pp-number E sign
pp-number p sign
pp-number P sign
pp-number .

Here is no " ", so thats why i thought it is parsed as:

0xe foo

What am I missing? I know the rule of maximum match, but how is the " " sign a pp-number?

If I would have x y it is parsed as x y, which makes sense, but how is then 0xe foo not parsed as 0xe foo?

CodePudding user response：

matches sign in the production you quoted.