小数の比較

fraction.cpp

#include <bits/stdc++.h>
using namespace std;

void f(string A, string X, string Y){
    cout << "a, x, y = " << A << ", " << X << ", " << Y << "\n";
    double dA=stod(A), dX=stod(X), dY=stod(Y);
    long double ldA=stold(A), ldX=stold(X), ldY=stold(Y);
    long lA=stol(A), lX=stol(X), lY=stol(Y);
    /* 入力をdoubleで比較 */
    if ((dA/dX) == (dA/dY)) cout << "double            : a/x == a/y" << "\n";
    if ((dA/dX) >  (dA/dY)) cout << "double            : a/x >  a/y" << "\n";
    if ((dA/dX)  < (dA/dY)) cout << "double            : a/x  < a/y" << "\n";
    /* 入力をlong doubleで比較 */
    if ((ldA/ldX) == (ldA/ldY)) cout << "long double       : a/x == a/y" << "\n";
    if ((ldA/ldX) >  (ldA/ldY)) cout << "long double       : a/x >  a/y" << "\n";
    if ((ldA/ldX)  < (ldA/ldY)) cout << "long double       : a/x  < a/y" << "\n";
    /* 入力をlongにいれて通分して比較 */
    if ((lA*lY) == (lA*lX)) cout << "Common long       : a/x == a/y (means: a*y == a*x)" << "\n";
    if ((lA*lY) >  (lA*lX)) cout << "Common long       : a/x >  a/y (means: a*y == a*x)" << "\n";
    if ((lA*lY)  < (lA*lX)) cout << "Common long       : a/x  < a/y (means: a*y == a*x)" << "\n";
    /* 入力をdoubleにいれて通分して比較 */
    if ((dA*dY) == (dA*dX)) cout << "Common      double: a/x == a/y (means: a*y == a*x)" << "\n";
    if ((dA*dY) >  (dA*dX)) cout << "Common      double: a/x >  a/y (means: a*y == a*x)" << "\n";
    if ((dA*dY)  < (dA*dX)) cout << "Common      double: a/x  < a/y (means: a*y == a*x)" << "\n";
    /* 入力をlong doubleにいれて通分して比較 */
    if ((ldA*ldY) == (ldA*ldX)) cout << "Common long double: a/x == a/y (means: a*y == a*x)" << "\n";
    if ((ldA*ldY) >  (ldA*ldX)) cout << "Common long double: a/x >  a/y (means: a*y == a*x)" << "\n";
    if ((ldA*ldY)  < (ldA*ldX)) cout << "Common long double: a/x  < a/y (means: a*y == a*x)" << "\n";
}
int main() {
    /* X,Yは1e16+(1,2,3,4)です。このため、 以下の入力ではAX, AY <=1e17です。 */
    cout << "C++\n";
    f("1", "10000000000000001", "10000000000000002");
    f("1", "10000000000000003", "10000000000000004");
    f("5", "10000000000000001", "10000000000000002");
    f("5", "10000000000000003", "10000000000000004");
}