How Can I Accurately Round Floating-Point Numbers in C ?

Rounding Floating-Point Values in C with round()

To round floating-point values accurately in C , one can employ the versatile round() function. This function performs the rounding operation based on the specified rounding rule and is essential for scenarios where floating-point values need to be rounded with precision.

While C 98, the earlier version of the C standard, lacks a native round() function, one can write their own implementation. A common approach is to implement the round-half-up rule, which can be realized with the following code:

double round(double d) {
  return floor(d + 0.5);
}

This implementation reflects the standard rounding behavior where values less than or equal to -0.5 are rounded down, while values greater than -0.5 are rounded up.

It's important to note that round-half-up is not the only rounding rule. Round-to-even, for instance, is an alternative method that aims to avoid bias and is preferred in scenarios involving repeated rounding. Implementing round-to-even requires a slightly more complex algorithm.

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