{"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":"

The “anchored” 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

For example, consider an unanchored regular expression, which matches any part of a string:<\/p>\n

\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
\ncopyright: String = Copyright 2016\n<\/pre>\n
We can force this to match the whole string (which will fail for our example string):<\/p>\n
\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
\ncopyright: String = No match\n<\/pre>\n
This is essentially equivalent to adding ^ and $ inside the regular expression, to forece matching the string to the beginning and end:<\/p>\n
\nval date = \"\"\"^(\\d\\d\\d\\d)$\"\"\".r\n<\/pre>\n
When you call “anchored” you can reverse the effect with the “unanchored” function:<\/p>\n
\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
\ncopyright: String = Copyright 2016\n<\/pre>\n
However, “unanchored” and “anchored” just set an internal flag – they don’t consider the regular expression itself, so they will not remove the effects of ^ and $ in the regular expression:<\/p>\n
\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
\ncopyright: String = No match\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
Using the “anchored” 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,"footnotes":""},"categories":[4],"tags":[460,480],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t