pcb@usl.usl.edu (Peter C. Bahrs) (11/14/88)
We are programming in Microsoft C v5.1 and MS Windows 2.03.
We are trying to convert a double precision number which represents
a delta time into a string which represents military time using the
"modf" function.
Example:
double dTime = 101.1;
double dt, dTemp, dMinutes, dHours, dSeconds;
/* Below is the results */
dt = fmod (dTime, (double) 24.0); /* dt now equals 5.1 */
dTemp = modf (dt, &dHours) * 60.0; /* dtemp = 6.0, dHours = 5.0 */
dSeconds = modf (dTemp, &dMinutes) * 60.0; /* dSeconds = 60.0, dMinutes = 5.0 */
sprintf (szBuff, "%02d:%02d:%02d", (int)dHours, (int)dMinutes, (int)dSeconds);
Now szBuff is 05:05:59? the correct answer should be 05:06:00
Question: Why is modf returning a 1.0 when calculating dSeconds? The
docs say that the return value is the fractional portion.
Comment: We have printed every possible format of the double variables
to see if some residue was in the number (i.e. 6.000000000001) but
did not find anything.
I suspect some kind of representational problem in the compiler?
So.....!, the moral of the story is modf is returning a 1 !!!!!!! when
it should return 0.
Thanks in Advance
pcb@usl.usl.edu csnet