Replacing squotes with dquotes. Diff on GH: https://github.com/franckverrot/ruby/pull/1

0001-parse.y-Replace-squotes-with-dquotes.patch

From 739265f2f2c54d8be56ad58d7c863193f0ce472d Mon Sep 17 00:00:00 2001
From: Franck Verrot <[email protected]>
Date: Thu, 26 May 2016 10:12:29 -0700
Subject: [PATCH] * parse.y : Replace squotes with dquotes

---
 parse.y | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/parse.y b/parse.y
index 005e926..1752d3b 100644
--- a/parse.y
+++ b/parse.y
@@ -6560,7 +6560,7 @@ parser_heredoc_identifier(struct parser_params *parser)
     }
     switch (c) {
       case '\'':
-	func |= str_squote; goto quoted;
+	func |= str_dquote; goto quoted;
       case '"':
 	func |= str_dquote; goto quoted;
       case '`':
@@ -7739,7 +7739,7 @@ parse_percent(struct parser_params *parser, const int space_seen, const enum lex
 	    return tSTRING_BEG;
 
 	  case 'q':
-	    lex_strterm = NEW_STRTERM(str_squote, term, paren);
+	    lex_strterm = NEW_STRTERM(str_dquote, term, paren);
 	    return tSTRING_BEG;
 
 	  case 'W':
@@ -8411,7 +8411,7 @@ parser_yylex(struct parser_params *parser)
 
       case '\'':
 	label = (IS_LABEL_POSSIBLE() ? str_label : 0);
-	lex_strterm = NEW_STRTERM(str_squote | label, '\'', 0);
+	lex_strterm = NEW_STRTERM(str_dquote | label, '\'', 0);
 	return tSTRING_BEG;
 
       case '?':
-- 
2.7.3

concatenation.rb

# courtesy of https://github.com/JuanitoFatas/fast-ruby/blob/master/code/string/concatenation.rb
require 'benchmark/ips'

# 2 + 1 = 3 object
def slow_plus
  'foo' + 'bar'
end

# 2 + 1 = 3 object
def slow_concat
  'foo'.concat 'bar'
end

# 2 + 1 = 3 object
def slow_append
  'foo' << 'bar'
end

# 1 object
def fast
  'foo' 'bar'
end

def fast_interpolation
  "#{'foo'}#{'bar'}"
end

Benchmark.ips do |x|
  x.report('String#+')                 { slow_plus }
  x.report('String#concat')            { slow_concat }
  x.report('String#append')            { slow_append }
  x.report('"foo" "bar"')              { fast }
  x.report('"#{\'foo\'}#{\'bar\'}"')   { fast_interpolation }
  x.compare!
end

with-patch.log

λ ruby concatenation.rb
Warming up --------------------------------------
            String#+    58.167k i/100ms
       String#concat    59.549k i/100ms
       String#append    60.170k i/100ms
         "foo" "bar"    79.179k i/100ms
  "#{'foo'}#{'bar'}"    81.362k i/100ms
Calculating -------------------------------------
            String#+    999.051k (± 3.8%) i/s -      5.002M in   5.014765s
       String#concat      1.082M (± 4.8%) i/s -      5.419M in   5.022983s
       String#append      1.140M (± 4.3%) i/s -      5.716M in   5.022578s
         "foo" "bar"      1.826M (± 4.8%) i/s -      9.106M in   4.999979s
  "#{'foo'}#{'bar'}"      1.789M (± 7.7%) i/s -      8.950M in   5.038771s

Comparison:
         "foo" "bar":  1825544.4 i/s
  "#{'foo'}#{'bar'}":  1788974.3 i/s - same-ish: difference falls within error
       String#append:  1140399.8 i/s - 1.60x slower
       String#concat:  1081619.8 i/s - 1.69x slower
            String#+:   999051.2 i/s - 1.83x slower

without-patch.log

~  [○] λ ruby /tmp/concatenation.rb
Warming up --------------------------------------
            String#+    56.174k i/100ms
       String#concat    59.173k i/100ms
       String#append    62.512k i/100ms
         "foo" "bar"    81.058k i/100ms
  "#{'foo'}#{'bar'}"    81.225k i/100ms
Calculating -------------------------------------
            String#+    964.524k (± 4.5%) i/s -      4.831M in   5.019469s
       String#concat      1.060M (± 4.6%) i/s -      5.326M in   5.036661s
       String#append      1.129M (± 4.1%) i/s -      5.689M in   5.048866s
         "foo" "bar"      1.825M (± 4.5%) i/s -      9.160M in   5.030873s
  "#{'foo'}#{'bar'}"      1.818M (± 4.9%) i/s -      9.097M in   5.018021s

Comparison:
         "foo" "bar":  1824600.9 i/s
  "#{'foo'}#{'bar'}":  1817629.8 i/s - same-ish: difference falls within error
       String#append:  1128802.6 i/s - 1.62x slower
       String#concat:  1059964.0 i/s - 1.72x slower
            String#+:   964524.3 i/s - 1.89x slower