Add bin and edit workflow

bin/gems/facets-3.1.0/lib/standard/facets/math/lngamma.rb

@@ -0,0 +1,18 @@
+module Math
+
+  # Logarithmus naturalis of gamma function of `x`.
+  # 
+  # Notice the use of `ln` prefix to differentiate from
+  # Ruby's built-in `#lgamma` function which returns an Array.
+  #
+  def self.lngamma(x)
+    lgamma(x).first
+  end
+
+  # Old name used by Extmath library.
+  def self.ln_gamma(x)
+    lgamma(x).first
+  end
+
+end
+