How to round a number to end in 50 in obj c or c++ / cocoa?
I am writing a tax program, for the final lookup i have to round the income to end in 50 before i apply the tax rate.
The only alternative i can think of is string modification, but im shaky in that area,].
It's unclear whether you want the nearest $50 or 50 cents, so here's both:
For an integer to go to a multiple of 50, you need the formula:
x = int(x / 50) * 50 ; for truncation.
x = int((x + 25) / 50) * 50 ; for rounding.
For an float to go to a multiple of 0.50, you need the formula:
x = 0.5 * int(x / 0.5) ; for truncation.
x = 0.5 * int((x + 0.25) / 0.5) ; for rounding.
Update:
If you just want the last two digits changed to 50, simply do one of:
x = x - (x % 100) + 50
x = 50 + 100 * int (x / 100)
Give a man a fish and he has food for one day.
What you want to know is how many 'chunks' of 50 are in a number. This can be achieved by floating point division.
const double chunksize = 50.;
const double chunks=income/chunksize;
Then, apparently, you get to an integer number of chunks, by rounding, truncating, ...
const int i_chunks = ceil( chunks );
And finally you want to scale the number of chunks back to the original currency:
const double chunked_income = i_chunks*chunksize;