Calculate log base 2 of a number in Kotlin

This article explores different ways to calculate the log₂ of a number in Kotlin.

1. Using `ln()` function

The idea is to use the ln(n) function to compute the natural logarithm (base e) of the value n and use the logarithmic identity to calculate log₂(n). The logarithmic identity is log_ba = log₁₀(a)/log₁₀(b), therefore, log₂n = log₁₀(n)/log₁₀(2). Note the following special cases as per the Kotlin docs:

ln(NaN) is NaN
ln(n) is NaN when n < 0.0
ln(+Inf) is +Inf
ln(0.0) is -Inf

Here's the working example:

import kotlin.math.ln

fun log2(n: Int): Double {

return ln(n.toDouble()) / ln(2.0)

}

fun main() {

val n = 10

val log2n = log2(n)

println(log2n)

}

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Output:

3.3219280948873626

2. Using `Integer.numberOfLeadingZeros()` function

The Integer.numberOfLeadingZeros() function returns the number of 0-bits preceding the most significant set bit. Then the log₂(n) for a number n can be derived using the formula: 31 - Integer.numberOfLeadingZeros(n).

fun log2(n: Int): Int {

require(n > 0) { "n ($n) must be positive" }

return 31 - Integer.numberOfLeadingZeros(n)

}

fun main() {

val n = 10

val log2n = log2(n)

println(log2n)

}

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Output:

3

That's all about calculating the log₂ of a number in Kotlin.

Calculate log base 2 of a number in Kotlin

1. Using ln() function

2. Using Integer.numberOfLeadingZeros() function

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1. Using `ln()` function

2. Using `Integer.numberOfLeadingZeros()` function