TITLE: Stream manipulators for oct and hex


PROBLEM: freeman@orville.psu.edu (Art Freeman)

Error messages:
t.cxx:18: error: In this statement, "ch" is of type "char", and may not be converted to "ios".
t.cxx:19: error: In this statement, "ch" is of type "char", and may not be converted to "ios".
Compilation terminated with errors. 


Program listing:
    15		char ch = alpha[i];
    16		cout << '\'' << ch << '\''
    17		     << " = " << int(ch)
    18		     << " = 0" << oct(ch)
    19		     << " = 0x" << hex(ch) << '\n';


RESPONSE: steve@taumet.com (Steve Clamage), 8 Feb 93

Your problem is that 'oct' and 'hex' are defined in <iostream.h> as
manipulators:
	ios& oct(ios&);
	ios& hex(ios&);
With no other declarations visible, the compiler must try to convert
the char argument to ios&, which can't be done.

You may be trying to use the old-style (C++ 1.3) formatting functions
	char* oct(long, int=0);
	char* hex(long, int=0);
which are not always supplied with current C++ implementations.

You can get the effect you want like this:
	<< oct << int(ch)
	<< hex << int(ch)

Bear in mind that the conversion base of the stream is changed by
the manipulators and remains until explicitly changed again.  You
could add
	cout << dec;
to restore the decimal base, or use the setf() functions.