A few clojure java regex samples

re.clj

(def ptrn
  {
   :a {:pattern #"a(?!b)"
       :purpose "Only allow a if it is not preceded by a 'b' (negative lookahead)"
       :samples ["acdefg" ; ok
                 "abcdef" ; nil
                 ]}
   
   :b {:pattern #"(?i)(<title.*?>)(.+?)(</title>)"
       :purpose "Grouping and backreference to get the text from a HTML <title> tag."
       :samples ["titles are just dumb" ; nil
                 "<title>1337</title>"  ; ok
                 ]}
   
   :c {:pattern #"(\w)(\s+)([\.,])"
       :purpose "Remove whitespace between word and . or ,"
       :samples ["word ." ; ok
                 "to ,"   ; ok
                 "test."  ; nil
                 ]}
   :d {:pattern #"[a-zA-Z]{3}"
       :purpose "Get exactly 3 characters from A to Z in both upper- and lower-case. Not less."
       :samples ["FU"   ; nil
                 "John" ; Joh
                 "Joe"  ; Joe
                 ]}
   
   :e {:pattern #"[tT]rue|[yY]es"
       :purpose "returns true if the string matches exactly 'true' or 'True' or 'yes' or 'Yes"
       :samples [""      ; ?
                 ""      ; ?
                 ""      ; ?
                 ]}
   
   :f {:pattern #"^[^\d].*"
       :purpose "Returns true if the string does not have a number at the beginning"
       :samples ["1 beer please"          ; nil
                 "More beer for this 1!!" ; ok
                 "One beer two beer"      ; ok
                 ]}
   
   :g {:pattern #"[^0-9]*[12]?[0-9]{1,2}[^0-9]*"
       :purpose "Returns true if the string contains a number less then 300"
       :samples  ["123456789101112134"      ; ok
                 "Someone rented 300"      ; ?
                 "99 bottles of beer"      ; ?
                 ]}
   
   :h {:pattern #"([\w&&[^b]])*"
       :purpose "Returns true if the string contains a arbitrary number of characters except b"
       :samples  ["acdefghijklmnopqrstuvwxyz"      ; ok
                  "ABBA was a mid 70's band"       ; nil
                  "Berenbotje kon niet varen"      ; nil
                  ]}
   
   ;;
   
   
   
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   :X {:pattern #""
       :purpose ""
       :samples [""      ; ?
                 ""      ; ?
                 ""      ; ?
                 ]}
   
   
   })

(defn step [k] (map #(re-matches (get-in ptrn [k :pattern]) %) (get-in ptrn [k :samples])))



;; Java built-in regex support in string objects

;; A little threading macro to show how string instances have native
;; methods to deal with regular expressions.
(-> "foo bar" String. (.matches "fo.*"))





(step :h)