Doubles are giving me problems

Posted on 16th Feb 2014 by admin

Ok so, first of all i made a double = 0.05, but when running the debugger it shows up as 0.04999. I know this has something to do with how doubles store but its causing problems for me. Anyway, in the code I'm trying to get only the right hand side(rhs) of the double variable jdn's decimal point. So in the code example I'm only trying to get .05. But rhs isn't always going to be the same and can have up to 0.00005 <- that fifth one there(can't remember what its called - hundred thousandth?). I have constant numbers right now for the sake of testing this. Now the counter goes through starting at 0.1, to make sure everything after the decimal point is 0. It goes through fine until it gets to 0.0002 - 0.0001 and then rhs = 9.99998e-005.
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#include #include #include using namespace std; int main() { double jdn = 2454115.05; double lhs = floor(jdn); double rhs = jdn - lhs; double counter = 0.1; if( rhs != 0.0 ) while( (rhs != 0.000001) || (counter != 0.00001) ) { if( (rhs - counter) <= 0 ) { counter *= 0.1; //cout << "rhs = " << rhs << endl; } else { rhs -= counter; cout << "rhs = " << rhs << endl; } } cout << "ok" << endl; return 0; }
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rhs = 0.04 rhs = 0.03 rhs = 0.02 rhs = 0.01 rhs = 0.009 rhs = 0.008 rhs = 0.007 rhs = 0.006 rhs = 0.005 rhs = 0.004 rhs = 0.003 rhs = 0.002 rhs = 0.001 rhs = 0.0009 rhs = 0.0008 rhs = 0.0007 rhs = 0.0006 rhs = 0.0005 rhs = 0.0004 rhs = 0.0003 rhs = 0.0002 rhs = 9.99998e-005