Rounding up and down a number C++

c++ cmath ceil
Teo Chuen Wei Bryan picture Teo Chuen Wei Bryan · Oct 7, 2016 · Viewed 49.1k times · Source

I'm trying to allow my program to round a number up and down respectively.

For example, if the number is 3.6, my program is suppose to round up the nearest number which is 4 and if the number is 3.4, it will be rounded down to 3.

I tried using the ceil library to get the average of 3 items.

results = ceil((marks1 + marks2 + marks3)/3)

However, the ceil only rounds the number down but does not roll the number up.

There's 1 algorithm i stumbled upon

var roundedVal = Math.round(origVal*20)/20;

but i still can't figure a formula for some problem.

Answer

brettmichaelgreen picture brettmichaelgreen · Oct 7, 2016 
std::ceil

rounds up to the nearest integer

std::floor

rounds down to the nearest integer

std::round

performs the behavior you expect

please give a use case with numbers if this does not provide you with what you need!

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