Add Hash#merge({}) vs Hash#dup#merge!({}) vs {}#merge!(Hash)

Author: bejmuller

code/hash/merge-vs-dup-merge-bang-vs-merge-bang.rb

@@ -0,0 +1,29 @@
+require 'benchmark/ips'
+
+ENUM = (1..100)
+ORIGINAL_HASH = { key1: 'value 1' }
+
+def slow
+  ENUM.inject([]) do |a, e|
+    a << ORIGINAL_HASH.merge(key2: e)
+  end
+end
+
+def slow_dup
+  ENUM.inject([]) do |a, e|
+    a << ORIGINAL_HASH.dup.merge!(key2: e)
+  end
+end
+
+def fast
+  ENUM.inject([]) do |a, e|
+    a << { key2: e }.merge!(ORIGINAL_HASH)
+  end
+end
+
+Benchmark.ips do |x|
+  x.report('Hash#merge({})') { slow }
+  x.report('Hash#dup#merge!({})') { slow_dup }
+  x.report('{}#merge!(Hash)') { fast }
+  x.compare!
+end