Round to the next 0.05 in C

Question

Consider a float value, such as 1.82 , set by the user. How to find the next highest value .05? For this example, the next highest value is 1.85.

Is there a simple way or complex algorithm required? I tried using the floor and ceiling functions to come up with the distance from the float to the next highest and lowest integer value. But I'm not sure how to act as soon as I have this information.

Thanks.

Answer 1

Multiply by 20, use the ceiling, divide by 20.

Answer 2

Excellent useful and informative resource for rounding methods .

Answer 3

Code for @Justin's answer. Please note that this is very easy to generalize.

 #include <math.h> #include <stdio.h> int main(void) { int i; double numbers[] = { 1.82, 0.3, 0.2, 0.5, 10000000000.849, }; for (i = 0; i < sizeof(numbers)/sizeof(numbers[0]); ++i) { double scaled = ceil(20 * numbers[i]); printf("%.2f\n", scaled/20.0); } return 0; } 

Answer 4

 float fixedCeil(float num, float factor) { float steps = 1.0f / factor; return ceil(steps*num)/steps; } assert(fixedCeil(2.43f, 0.05f) == 2.45f); 

(statement is simply fictitious)

Answer 5

You can use something like

  // Rounds X to the nearest Y double round(double x, double y) { return floor(x / y + 0.5) * y; }