{"id":4347,"date":"2016-06-05T01:29:04","date_gmt":"2016-06-05T01:29:04","guid":{"rendered":"http:\/\/www.garysieling.com\/blog\/?p=4347"},"modified":"2016-06-05T01:29:04","modified_gmt":"2016-06-05T01:29:04","slug":"scala-regex-anchored-example","status":"publish","type":"post","link":"https:\/\/www.garysieling.com\/blog\/scala-regex-anchored-example\/","title":{"rendered":"Scala regex anchored example"},"content":{"rendered":"<p>The <a href=\"https:\/\/www.garysieling.com\/scaladoc\/scala.util.matching.regex\/2016\/02\/15\/scala__util_matching_Regex.html\">&#8220;anchored&#8221; function<\/a> on a Scala regular expression forces the regular expression to match the entire string (i.e. anchored to the beginning and end of the string).<\/p>\n<p>For example, consider an unanchored regular expression, which matches any part of a string:<\/p>\n<pre lang=\"scala\">\nval date = \"\"\"(\\d\\d\\d\\d)\"\"\".r\n\nval copyright: String = \"Year: 2016\" match {\n  case date(year) => s\"Copyright $year\"\n  case _ => \"No match\"\n}\n<\/pre>\n<pre>\ncopyright: String = Copyright 2016\n<\/pre>\n<p>We can force this to match the whole string (which will fail for our example string):<\/p>\n<pre lang=\"scala\">\nval date = \"\"\"(\\d\\d\\d\\d)\"\"\".r.anchored\n\nval copyright: String = \"Year: 2016\" match {\n  case date(year) => s\"Copyright $year\"\n  case _ => \"No match\"\n}\n<\/pre>\n<pre>\ncopyright: String = No match\n<\/pre>\n<p>This is essentially equivalent to adding ^ and $ inside the regular expression, to forece matching the string to the beginning and end:<\/p>\n<pre lang=\"scala\">\nval date = \"\"\"^(\\d\\d\\d\\d)$\"\"\".r\n<\/pre>\n<p>When you call &#8220;anchored&#8221; you can reverse the effect with the &#8220;unanchored&#8221; function:<\/p>\n<pre lang=\"scala\">\nval date = \"\"\"(\\d\\d\\d\\d)\"\"\".r.anchored\n\nval copyright: String = \"Year: 2016\" match {\n  case date.unanchored(year) => s\"Copyright $year\"\n  case _ => \"No match\"\n}\n<\/pre>\n<pre>\ncopyright: String = Copyright 2016\n<\/pre>\n<p>However, &#8220;unanchored&#8221; and &#8220;anchored&#8221; just set an internal flag &#8211; they don&#8217;t consider the regular expression itself, so they will not remove the effects of ^ and $ in the regular expression:<\/p>\n<pre lang=\"scala\">\nval date = \"\"\"^(\\d\\d\\d\\d)$\"\"\".r\n\nval copyright: String = \"Year: 2016\" match {\n  case date.unanchored(year) => s\"Copyright $year\"\n  case _ => \"No match\"\n}\n<\/pre>\n<pre>\ncopyright: String = No match\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Using the &#8220;anchored&#8221; function on a scala regular expression<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[4],"tags":[460,480],"aioseo_notices":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/posts\/4347"}],"collection":[{"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/comments?post=4347"}],"version-history":[{"count":0,"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/posts\/4347\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/media?parent=4347"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/categories?post=4347"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.garysieling.com\/blog\/wp-json\/wp\/v2\/tags?post=4347"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}