Issue #21527 has been updated by mame (Yusuke Endoh). I investigated how other languages name the `log1p` function: * `log1p`: Python, Java, JavaScript, Go, PHP, .NET, R, MATLAB, Kotlin, Swift, Julia, Haskell, OCaml, Crystal * `ln_1p`: Rust * Not natively provided (unless I missed it): Perl, Lua, Dart, Erlang As you can see, most languages provide this function under the name `log1p`. Rust uses a slightly different name, which is more cryptic to me :-) In fact, I first noticed Ruby didn't have "Math.log1p" when I tried to write code sample code written in Python into Ruby. Given this, I believe it's best to follow the common naming convention here. POSIX, libc, and many languages provide them. Needing FFI to access it in Ruby isn't ideal. https://docs.python.org/3.13/library/math.html#math.log1p https://numpy.org/devdocs/reference/generated/numpy.log1p.html https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Obj... https://docs.oracle.com/en/java/javase/24/docs/api/java.base/java/lang/Math....) https://pkg.go.dev/math#Log1p https://www.php.net/manual/en/function.log1p.php https://learn.microsoft.com/en-us/dotnet/api/java.lang.math.log1p?view=net-a... https://www.mathworks.com/help/matlab/ref/double.log1p.html https://doc.rust-lang.org/std/primitive.f64.html#method.ln_1p https://developer.android.com/reference/kotlin/java/lang/Math#log1p https://developer.apple.com/documentation/simd/log1p https://docs.julialang.org/en/v1/base/math/#Base.log1p https://hackage.haskell.org/package/base-4.21.0.0/docs/Numeric.html#v:log1p https://ocaml.org/manual/4.02/libref/Pervasives.html#VALlog1p https://crystal-lang.org/api/1.17.1/Math.html#log1p%28value%29-instance-meth... ---------------------------------------- Feature #21527: Proposal: Math.log1p and Math.expm1 https://bugs.ruby-lang.org/issues/21527#change-114230 * Author: mame (Yusuke Endoh) * Status: Open ---------------------------------------- Let's add `Math.log1p` and `Math.expm1`. * `Math.log1p(x)`: Computes `Math.log(x + 1)` * `Math.expm1(x)`: Computes `Math.exp(x) - 1` These methods are often more accurate than the straightforward computation, especially when `x` is close to zero. ``` # The current approach loses precision p Math.log(1 + 1.0e-16) #=> 0.0 p Math.exp(1.0e-16) - 1 #=> 0.0 # The proposed methods return the accurate result p Math.log1p(1.0e-16) #=> 1.0e-16 p Math.expm1(1.0e-16) #=> 1.0e-16 ``` Note that they are very standard; the C99 even defines `log1p()` and `expm1()`. Other major programming languages (Python, JavaScript, Java, Go, Rust, etc.) also provide them. PR: https://github.com/ruby/ruby/pull/14087 -- https://bugs.ruby-lang.org/