11. Put that character back!!!

• What if we need a function that can

  1. check next character;

  2. if necessary, put the character back into the input buffer.

  This allows to have functions sensitive to various types of input.

• For example, program cin_unget_char.cpp ( download ) illustrates:

  • stand-alone function named get_value( ) to input a single integer

  • main( ) function that reports an error to the user. That is, the user dialog is separated from the get_value( ) function.

  • cin.unget()
    call to put the last character back into the input buffer.

  • cin.clear( ios_base::failbit )
    call, which transitions cin object into the state corresponding to cin.fail().