Use methods instead of hash.

Closes fastruby#100

README.md

@@ -1008,17 +1008,15 @@ Comparison:
 
 ```
 $ ruby -v code/string/mutable_vs_immutable_strings.rb
-ruby 2.2.1p85 (2015-02-26 revision 49769) [x86_64-darwin14]
-Warming up --------------------------------------
-              freeze   111.292k i/100ms
-              normal   106.928k i/100ms
+ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin14]
+
 Calculating -------------------------------------
-              freeze      5.282M (±14.2%) i/s -     25.931M
-              normal      4.549M (±14.3%) i/s -     22.348M
+      Without Freeze      7.279M (± 6.6%) i/s -     36.451M in   5.029785s
+         With Freeze      9.329M (± 7.9%) i/s -     46.370M in   5.001345s
 
 Comparison:
-              freeze:  5281661.4 i/s
-              normal:  4548975.9 i/s - same-ish: difference falls within error
+         With Freeze:  9329054.3 i/s
+      Without Freeze:  7279203.1 i/s - 1.28x slower
 ```
 
 

code/string/mutable_vs_immutable_strings.rb

@@ -1,12 +1,17 @@
-require 'benchmark/ips'
+require "benchmark/ips"
 
-IMMUTABLE_TEST = "writing_fast_ruby".freeze
-mutable_test = "writing_fast_ruby"
+# Allocates new string over and over again
+def without_freeze
+  "To freeze or not to freeze"
+end
 
-hash = {"writing_fast_ruby" => "is_cool"}
+# Keeps and reuses shared string
+def with_feeze
+  "To freeze or not to freeze".freeze
+end
 
 Benchmark.ips do |x|
-  x.report("freeze") { hash[IMMUTABLE_TEST] }
-  x.report("normal") { hash[mutable_test] }
+  x.report("Without Freeze") { without_freeze }
+  x.report("With Freeze") { with_feeze }
   x.compare!
 end