Hello:
Is it possible to declare a variable with multiple data types.
for example in my program I would like to declare my variable as int or char depending on the situation the variable is in as an example.
declare variable C
int K =cin();
if( K ==4)
C = 5;
else
C = '*'
thanks
You can't change the data type of a variable.
try this:
#include <iostream>
using namespace std;
int main() {
char var;
char choice;
clog << "do you want the variable to be int or char? type i for int and c for char.\n";
cin >> choice;
clog << "what number or char do you want displayed?\n";
cin >> var;
if(choice == 'i')
clog << "\n" << (int) var - 48 << "\n";
else
clog << "\n" << var << "\n";
return 0;
}You can't really change a variable unless you cast it into something else. In the example I cast the char to int and subtract 48 because if you look at the ASCII table (http://www.asciitable.com/) , thats how much the character 0 and the integer 0 are offset by.
I can't think of any really simple way to do this. I suppose you could use something like a struct or a union. This way you could store more than one type of variable depending on what you need. I was thinking something like:
#include <iostream>
using namespace std;
struct Data
{
int a;
char b;
Data();
};
Data::Data()
{
a = 0;
b = '\0';
}
int main()
{
Data data;
string temp;
cout << "Enter some data -> ";
cin >> temp;
if (temp == "4")
{
data.a = 4;
}
else
{
data.b = '*';
}
cout << data.a << endl << data.b << endl;
return 0;
}Not an ideal solution, but it works.
Thank you all for your reply....
What about using a template <typedef> T
T somenumer
Unfortunately typedef templates aren't supported by the C++98 standard. Here's a way you could convert a 3 digit string into the corresponding 3 digit integer:
#include <iostream>
#include <string>
using namespace std;
int main() {
string numstr;
clog << "enter 3 digit number\n";
cin >> numstr;
int numint = ((numstr[0] - 48) * 100) + ((numstr[1] - 48) * 10) + (numstr[2] - 48);
clog << "number in integer form: " << numint << "\n";
clog << "number in string form: " << numstr << "\n";
return 0;
}but yeah.. sorry I guess that really doesn't answer your question. Do you HAVE to set that same variable to '*'. There might be an easier work around depending on your application.
C language doesn't have a real character data type. char is just a one-byte integer, and all characters such as '=' are treated exactly like integers. You can safely assign '=' to either a char or int data type (also long, long long, __int64, float or double).
You can also perform mathematical operations with characters, such as int numint = ((numstr[0] - '0') * 100) + ((numstr[1] - '0') * 10) + (numstr[2] - '0');
This sounded interesting so I made a class that changes its type,
simulates it at least.
I know there are some bugs, but its getting late ( 3 am). Anyways,
it could do the basic things a primitive datatype can to for now,
that is add,subtract,multiply,divide. It can also be used with
cin/cout, or ostream/istream;
Anyways here you are. You can disregard its implementation, and just use it.
I have an example below :
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
namespace Type
{
using namespace std;
class Variable
{
string var;
ostream& strm;
public:
Variable() : strm(cout), var(""){ }
template<typename T >
Variable(T a, std::ostream& os = cout) : strm(os),var("") {
var = this->changeType( a );
}
template<typename U>
string changeType(const U val ){
stringstream converter;
converter << val;
return converter.str();
}
//operator overloading
template<typename T>
Variable operator+(const T a)
{
stringstream ss;
T d;
ss << var;
ss >> d;
ss.clear();
ss.str("");
T r = d + a;
ss << r;
Variable tmp(ss.str());
return tmp;
}
Variable operator+(const Variable& v){
stringstream ss;
double d;
ss << v.var;
ss >> d;
return operator+(d);
}
template<typename T>
void operator+=(const T a){
string tmp = "";
tmp = this->operator +(a);
var = tmp;
}
template<typename T>
Variable operator-(const T a){
return this->operator +(-a);
}
Variable operator-(const Variable v){
stringstream ss;
double d = 0.0;
ss << v;
ss >> d;
return this->operator +(-d);
}
Variable operator-(const string s) {
Variable tmp(s); return this->operator-(tmp);
}
Variable operator-(){
Variable tmp(var);
stringstream ss;
double d;
ss << var;
ss >> d;
tmp = -d;
return tmp;
}
template<typename T>
void operator -=(const T a) {
string tmp = "";
tmp = this->operator -(a);
var = tmp;
}
template<typename T>
Variable operator /(const T a)
{
stringstream ss;
T d;
ss << var;
ss >> d;
ss.clear();
ss.str("");
T r = d / a;
ss << r;
Variable t( ss.str());
return t;
}
template<typename T>
void operator /=(const T a){
string tmp = "";
tmp = this->operator /(a);
var = tmp;
}
template<typename T>
Variable operator *(const T a){
if(!a || !var[0])
return "0";
string tmp = var;
string orig = var;
stringstream ss(var);
T add;
ss >> add;
for(int i = 1; i < a; i++) {
tmp = this->operator +(add);
var = tmp;
}
//reset val;
var = orig;
Variable t( tmp );
return t;
}
template<typename T>
void operator *=(const T a){
string tmp = "";
tmp = this->operator *(a);
var = tmp;
}
template<typename T>
void operator = (const Variable& a)
{
if(var != a.var)
var = a.var;
}
template<typename T>
void operator = (T a){
var = "";
var = this->changeType(a);
}
operator string() { return var; }
//Friend
friend ostream& operator<<(ostream& os,const Variable& v ){
os << v.var;
return os;
}
friend istream& operator>>(istream &stream, Variable &v)
{
stream >> v.var;
return stream;
}
template<typename T>
friend Variable operator*( T a, Variable& v) {
return v * a;
}
template<typename T>
friend Variable operator*=(T a, Variable& v) { return v *= a; }
template<typename T>
friend Variable operator/(T a, Variable& v) { return v / a; }
template<typename T>
friend Variable operator/=(T a, Variable& v) { return v /= a; }
template<typename T>
friend Variable operator+(T a, Variable& v) { return v + a; }
template<typename T>
friend Variable operator+=(T a, Variable& v) { return v += a; }
template<typename T>
friend Variable operator-(T a, Variable& v) { return v - a; }
template<typename T>
friend Variable operator-=(T a, Variable& v) { return v -= a; }
};
}
int main()
{
using namespace Type;
Variable X("hello");
cout << X << endl;
X.changeType(3.1415);
cout << X << endl;
X = 100/200.0;
cout<< X << endl;
cout<<"Enter a number : ";
cin >> X;
cout<< X <<" * 7 is = " << X*7;
return 0;
}No it does not have to be '*' but something to represent a null character so it does not have to be a char but I was curious if you could change a data type on the fly.
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