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cfunctionroundingfloor

Rounding down a floating point number to an integer value without a floor function in C

I need to write a function in C that rounds down a floating point number to an integer. For example, 10.6 becomes 10. 22.1249 becomes 22. However, I can't use a floor function. Can this be done?

Solution

  • Floor

    Use integer cast to round down float number.

    float yourFloat = 10.5;
int down = (int)yourfloat; //down = 10.

    Nearest integer

    To round to the nearest integer, add 0.5f to your float, then cast.

    float f1 = 10.3, f2 = 10.8;
int i1, i2;
i1 = (int)(f1 + 0.5f); //i1 = 10
i2 = (int)(f2 + 0.5f); //i2 = 11

    Ceil

    To round number up, use if statement with some casts:

    int result = (int)yourFloat;
if (yourFloat - (int)yourFloat > 0) {
    result++;
}