log2() function in C++ with Examples Last Updated : 04 May, 2020 Comments Improve Suggest changes Like Article Like Report The function log2() of cmath header file in C++ is used to find the logarithmic value with base 2 of the passed argument. Syntax: log2(x) Parameters: This function takes a value x, in the range [0, ∞] whose log value is to be found. Return Type: It returns the logarithmic value, as double, float or long double type, based on the following conditions: If x > 1: It returns the positive logarithmic value of x. If x is equals to 1: It returns 0. If 0 < x < 1: It returns the negative logarithmic value of x. If x is equals to 0: It returns the negative infinity(-∞). If x < 0: It returns NaN(Not a Number). Below examples demonstrate the use of log2() method: Example 1: CPP // C++ program to illustrate log2() function #include <bits/stdc++.h> using namespace std; // Driver Code int main() { long b = 16; float c = 2.5; double d = 10.35; long double e = 25.5; // Logarithmic value of long datatype cout << log2(b) << "\n"; // Logarithmic value of float datatype cout << log2(c) << "\n"; // Logarithmic value of double datatype cout << log2(d) << "\n"; // Logarithmic value of long double datatype cout << log2(e) << "\n"; return 0; } Output: 4 1.32193 3.37156 4.67243 Example 2: CPP // C++ program to illustrate log2() function #include <bits/stdc++.h> using namespace std; // Driver Code int main() { // To show extreme cases int a = 0; int b = -16; // Logarithmic value of 0 cout << log2(a) << "\n"; // Logarithmic value of negative value cout << log2(b) << "\n"; return 0; } Output: -inf nan Reference: http://www.cplusplus.com/reference/cmath/log2/ Comment More infoAdvertise with us Next Article log2() function in C++ with Examples A akash_garg Follow Improve Article Tags : C++ CPP-Functions cpp-math Practice Tags : CPP Similar Reads norm() function in C++ with Examples The norm() function is defined in the complex header file. 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