diff --git a/examples/character-or-string-width.rb b/examples/string_width.rb
similarity index 65%
rename from examples/character-or-string-width.rb
rename to examples/string_width.rb
index de60c358..b08e0fa1 100644
--- a/examples/character-or-string-width.rb
+++ b/examples/string_width.rb
@@ -1,38 +1,39 @@
-require 'rubygems'
-require 'ttfunk'
-require 'valuable'
+# frozen_string_literal: true
+
 # Everything you never wanted to know about glyphs:
 # http://chanae.walon.org/pub/ttf/ttf_glyphs.htm
 
 # this code is a substantial reworking of:
 # https://github.com/prawnpdf/ttfunk/blob/master/examples/metrics.rb
 
+require 'ttfunk'
+
 class Font
   attr_reader :file
 
   def initialize(path_to_file)
     @file = TTFunk::File.open(path_to_file)
   end
-  
-  def width_of( string )
-    string.split('').map{|char| character_width( char )}.inject{|sum, x| sum + x}
+
+  def width_of(string)
+    string.split('').sum { |char| character_width(char) }
   end
 
-  def character_width( character )
-    width_in_units = ( horizontal_metrics.for( glyph_id( character )).advance_width )
+  def character_width(character)
+    width_in_units = horizontal_metrics.for(glyph_id(character)).advance_width
     width_in_units.to_f / units_per_em
   end
 
   def units_per_em
-    @u_per_em ||= file.header.units_per_em
+    @units_per_em ||= file.header.units_per_em
   end
 
   def horizontal_metrics
-    @hm = file.horizontal_metrics
+    @horizontal_metrics ||= file.horizontal_metrics
   end
 
   def glyph_id(character)
-    character_code = character.unpack("U*").first
+    character_code = character.unpack1('U*')
     file.cmap.unicode.first[character_code]
   end
 end