Node:Unreading Idea, Next:, Up:Unreading



What Unreading Means

Here is a pictorial explanation of unreading. Suppose you have a stream reading a file that contains just six characters, the letters foobar. Suppose you have read three characters so far. The situation looks like this:

f  o  o  b  a  r
         ^
so the next input character will be b. If instead of reading b you unread the letter o, you get a situation like this:
f  o  o  b  a  r
         |
      o--
      ^
so that the next input characters will be o and b. If you unread 9 instead of o, you get this situation:
f  o  o  b  a  r
         |
      9--
      ^
so that the next input characters will be 9 and b.