Problém s sčítáním – C / C++ – Fórum – Programujte.com

Zdravim, pokud zadám a=66.55 tak r1 vychází správně ale r2 ne (r2 by se mělo rovnat 0, ale vychází 3,05...). Nevíte v čem je problém?

cin >> d;
cin >> a;
if(d==172){
                   r1=23.45+90-a;
                   r2=23.45-90+a;
                   cout << r2;
                  
                   if(c==0){                                                       
                            if (a==90){
                               cout << endl << "\t" << r1 << " severni sirky";}
                            if (a<90 && a>66.55){
                               cout << endl << "\t" << r1 << " severni sirky";
                               cout << endl << "\t" << r2 << " severni sirky";}
                            if (a==66.55){
                               cout << endl << "\t" << r1 << " severni sirky";
                               cout << endl << "\t" << r2 << " rovnik";}
                            if (a<66.55 && a>23.45){
                               cout << endl << "\t" << r1 << " severni sirky";
                               cout << endl << "\t" << -r2 << " jizni sirky";}
                            if (a==23.45){
                               cout << endl << "\t" << r1 << " severni sirky";
                               cout << endl << "\t" << -r2 << " jizni sirky";}
                            if (a<23.45){
                               cout << endl << "\t" << -r2 << " jizni sirky";}}

myslis jako 3.05176e-06  to jest:   0.0000305176   ??

#1 lukaswx
#2 KIIV
jj, ale mělo by to být 0 ne?

teoreticky ano ale pocitace maji urcity zpusob reprezentace realnych cisel, ktery proste z principu nedovoluje mit vetsi presnost nez na urcity pocet desetinnych mist ... cim mensi kladne cislo tim presnejsi je... cim je vetsi tim mene presne je...

muzes akorat prehodit float na double a zapnout zaokrouhlovani na urcity pocet desetinnych mist... treba na 5 by to byla opravdu presne nula :)

EDIT: jo double vychazi lip

#4 KIIV
stačilo dát double a vyhodilo to 0, děkuju :)

ale na to, ze je tam nula se nemuzes nikdy spolehnout :D