How to Calculate Logarithm Base 2 (log2) in C/C ?

Calculating Logarithm Base 2 in C/C

In C and C , there exists no built-in function specifically for calculating the logarithm base 2 (log2). While functions like log() for base e and log10() for base 10 are readily available, log2() is not directly provided.

Solution: Mathematical Transformation

To overcome this limitation, one can rely on a simple mathematical conversion. The formula to calculate log2 is as follows:

log2(x) = log(x) / log(2)

where:

• log(x) is the natural logarithm (base e)
• log(2) is the constant value of approximately 0.693

Using Built-in Functions

Using the above formula, you can implement the log2() function using the built-in log() function:

C :

<code class="cpp">double log2(double x) {
    return log(x) / log(2);
}</code>

C:

<code class="c">double log2(double x) {
    return log(x) / log(2.0);
}</code>

Example Usage:

<code class="cpp">#include <iostream>
#include <math.h>

int main() {
    double x = 10;
    double log2_result = log2(x);
    std::cout << "log2(" << x << ") = " << log2_result << std::endl;

    return 0;
}</code>

Output:

log2(10) = 3.321928

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