Simplified strong/emphasis regexps

(?<=\S|^) becomes (?<!\s)
(?=\S|$)  becomes (?!\s)
(?<!\s)(?<!\*) becomes (?<![\s*])
(?<!\s)(?<!_)  becomes (?<![\s_])
(?!\s)(?![\.,:;]\s) becomes (?![\.,:;]?\s)

Author: JoshyPHP

Michelf/Markdown.php

@@ -979,19 +979,19 @@ protected function makeCodeSpan($code) {
 
 
 	protected $em_relist = array(
-		''  => '(?:(?<!\*)\*(?!\*)|(?<!_)_(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'*' => '(?<=\S|^)(?<!\*)\*(?!\*)',
-		'_' => '(?<=\S|^)(?<!_)_(?!_)',
+		''  => '(?:(?<!\*)\*(?!\*)|(?<!_)_(?!_))(?![\.,:;]?\s)',
+		'*' => '(?<![\s*])\*(?!\*)',
+		'_' => '(?<![\s_])_(?!_)',
 		);
 	protected $strong_relist = array(
-		''   => '(?:(?<!\*)\*\*(?!\*)|(?<!_)__(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'**' => '(?<=\S|^)(?<!\*)\*\*(?!\*)',
-		'__' => '(?<=\S|^)(?<!_)__(?!_)',
+		''   => '(?:(?<!\*)\*\*(?!\*)|(?<!_)__(?!_))(?![\.,:;]?\s)',
+		'**' => '(?<![\s*])\*\*(?!\*)',
+		'__' => '(?<![\s_])__(?!_)',
 		);
 	protected $em_strong_relist = array(
-		''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<!_)___(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'***' => '(?<=\S|^)(?<!\*)\*\*\*(?!\*)',
-		'___' => '(?<=\S|^)(?<!_)___(?!_)',
+		''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<!_)___(?!_))(?![\.,:;]?\s)',
+		'***' => '(?<![\s*])\*\*\*(?!\*)',
+		'___' => '(?<![\s_])___(?!_)',
 		);
 	protected $em_strong_prepared_relist;
 
@@ -2837,19 +2837,19 @@ protected function _doFencedCodeBlocks_newlines($matches) {
 	# work in the middle of a word.
 	#
 	protected $em_relist = array(
-		''  => '(?:(?<!\*)\*(?!\*)|(?<![a-zA-Z0-9_])_(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'*' => '(?<=\S|^)(?<!\*)\*(?!\*)',
-		'_' => '(?<=\S|^)(?<!_)_(?![a-zA-Z0-9_])',
+		''  => '(?:(?<!\*)\*(?!\*)|(?<![a-zA-Z0-9_])_(?!_))(?![\.,:;]?\s)',
+		'*' => '(?<![\s*])\*(?!\*)',
+		'_' => '(?<![\s_])_(?![a-zA-Z0-9_])',
 		);
 	protected $strong_relist = array(
-		''   => '(?:(?<!\*)\*\*(?!\*)|(?<![a-zA-Z0-9_])__(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'**' => '(?<=\S|^)(?<!\*)\*\*(?!\*)',
-		'__' => '(?<=\S|^)(?<!_)__(?![a-zA-Z0-9_])',
+		''   => '(?:(?<!\*)\*\*(?!\*)|(?<![a-zA-Z0-9_])__(?!_))(?![\.,:;]?\s)',
+		'**' => '(?<![\s*])\*\*(?!\*)',
+		'__' => '(?<![\s_])__(?![a-zA-Z0-9_])',
 		);
 	protected $em_strong_relist = array(
-		''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<![a-zA-Z0-9_])___(?!_))(?=\S|$)(?![\.,:;]\s)',
-		'***' => '(?<=\S|^)(?<!\*)\*\*\*(?!\*)',
-		'___' => '(?<=\S|^)(?<!_)___(?![a-zA-Z0-9_])',
+		''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<![a-zA-Z0-9_])___(?!_))(?![\.,:;]?\s)',
+		'***' => '(?<![\s*])\*\*\*(?!\*)',
+		'___' => '(?<![\s_])___(?![a-zA-Z0-9_])',
 		);