Laboratory Exercises, C++ Programming

Strings and Streams 27
Note:
• Since the parameters are of type istream or ostream, the operator functions work for both
file streams and string streams.
• The functions are global “helper” functions. 7
• Both operators return the stream object that is the first argument to the operator, enabling
us to write, e.g., cout c;
if (c == ’(’) {
is >> re >> c;
if (c == ’,’) {
is >> im >> c;
if (c == ’)’) {
cplx = complex(re, im);
}
else {
// format error, set the stream state to ’fail’
is.setstate(ios_base::failbit);
}
}
else if (c == ’)’) {
cplx = complex(re, num_type(0));
}
else {
// format error, set the stream state to ’fail’
is.setstate(ios_base::failbit);
}
}
else {
is.putback(c);
is >> re;
cplx = complex(re, num_type(0));
}
return is;
}
}
7 The alternative implementation, to write operator>> and operator