What's the reverse of Math Power (**) in Ruby?

ruby math

The inverse of exponentiation is the logarithm. If a^b = c, then log_ac = b.

You can find logarithm functions in the Math module, specifically log() for base-e and log10() for base-10.

To get a logarithm to a different base (say n), use the formula log_Na = ^log_xa/_{log_xN}, where x is a value such as e or 10.

For your specific case:

log₂16 = ^log_e16/_{log_e2} = Math.log(16) / Math.log(2) = 4

Whether you consider the explanation good because it expands your knowledge, or bad because you hated high school math, is entirely up to you :-)

ruby math

Math.log(16) / Math.log(2)

ruby math

A cleaner way to obtain the logarithm, starting with Ruby 1.9.1, would be to use Math.log2:

[1] pry(main)> Math.log2(2**4)=> 4.0

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