string.clj

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(ns ^{:doc "Clojure String utilities

It is poor form to (:use clojure.string). Instead, use require
with :as to specify a prefix, e.g.

(ns your.namespace.here
  (:require [clojure.string :as str]))

Design notes for clojure.string:

1. Strings are objects (as opposed to sequences). As such, the
   string being manipulated is the first argument to a function;
   passing nil will result in a NullPointerException unless
   documented otherwise. If you want sequence-y behavior instead,
   use a sequence.

2. Functions are generally not lazy, and call straight to host
   methods where those are available and efficient.

3. Functions take advantage of String implementation details to
   write high-performing loop/recurs instead of using higher-order
   functions. (This is not idiomatic in general-purpose application
   code.)

4. When a function is documented to accept a string argument, it
   will take any implementation of the correct *interface* on the
   host platform. In Java, this is CharSequence, which is more
   general than String. In ordinary usage you will almost always
   pass concrete strings. If you are doing something unusual,
   e.g. passing a mutable implementation of CharSequence, then
   thead-safety is your responsibility."
      :author "Stuart Sierra, Stuart Halloway, David Liebke"}
  clojure.string
  (:refer-clojure :exclude (replace reverse))
  (:import (java.util.regex Pattern)
           clojure.lang.LazilyPersistentVector))

(defn ^String reverse
  "Returns s with its characters reversed."
  {:added "1.2"}
  [^CharSequence s]
  (.toString (.reverse (StringBuilder. s))))

(defn- replace-by
  [^CharSequence s re f]
  (let [m (re-matcher re s)]
    (let [buffer (StringBuffer. (.length s))]
      (loop []
        (if (.find m)
          (do (.appendReplacement m buffer (f (re-groups m)))
              (recur))
          (do (.appendTail m buffer)
              (.toString buffer)))))))

(defn ^String replace
  "Replaces all instance of match with replacement in s.

   match/replacement can be:

   string / string
   char / char
   pattern / (string or function of match).

   See also replace-first."
  {:added "1.2"}
  [^CharSequence s match replacement]
  (let [s (.toString s)]
    (cond 
     (instance? Character match) (.replace s ^Character match ^Character replacement)
     (instance? CharSequence match) (.replace s ^CharSequence match ^CharSequence replacement)
     (instance? Pattern match) (if (instance? CharSequence replacement)
                                 (.replaceAll (re-matcher ^Pattern match s)
                                              (.toString ^CharSequence replacement))
                                 (replace-by s match replacement))
     :else (throw (IllegalArgumentException. (str "Invalid match arg: " match))))))

(defn- replace-first-by
  [^CharSequence s ^Pattern re f]
  (let [m (re-matcher re s)]
    (let [buffer (StringBuffer. (.length s))]
      (if (.find m)
        (let [rep (f (re-groups m))]
          (.appendReplacement m buffer rep)
          (.appendTail m buffer)
          (str buffer))))))

(defn- replace-first-char
  [^CharSequence s ^Character match replace]
  (let [s (.toString s)
        i (.indexOf s (int match))]
    (if (= -1 i)
      s
      (str (subs s 0 i) replace (subs s (inc i))))))

(defn ^String replace-first
  "Replaces the first instance of match with replacement in s.

   match/replacement can be:

   char / char
   string / string
   pattern / (string or function of match).

   See also replace-all."
  {:added "1.2"}
  [^CharSequence s match replacement]
  (let [s (.toString s)]
    (cond
     (instance? Character match)
     (replace-first-char s match replacement)
     (instance? CharSequence match)
     (.replaceFirst s (Pattern/quote (.toString ^CharSequence match))
                    (.toString ^CharSequence replacement))
     (instance? Pattern match)
     (if (instance? CharSequence replacement)
       (.replaceFirst (re-matcher ^Pattern match s)
                      (.toString ^CharSequence replacement))
       (replace-first-by s match replacement))
     :else (throw (IllegalArgumentException. (str "Invalid match arg: " match))))))


(defn ^String join
  "Returns a string of all elements in coll, as returned by (seq coll),
   separated by an optional separator."
  {:added "1.2"}
  ([coll]
     (apply str coll))
  ([separator coll]
     (loop [sb (StringBuilder. (str (first coll)))
            more (next coll)
            sep (str separator)]
       (if more
         (recur (-> sb (.append sep) (.append (str (first more))))
                (next more)
                sep)
         (str sb)))))

(defn ^String capitalize
  "Converts first character of the string to upper-case, all other
  characters to lower-case."
  {:added "1.2"}
  [^CharSequence s]
  (let [s (.toString s)]
    (if (< (count s) 2)
      (.toUpperCase s)
      (str (.toUpperCase (subs s 0 1))
           (.toLowerCase (subs s 1))))))

(defn ^String upper-case
  "Converts string to all upper-case."
  {:added "1.2"}
  [^CharSequence s]
  (.. s toString toUpperCase))

(defn ^String lower-case
  "Converts string to all lower-case."
  {:added "1.2"}
  [^CharSequence s]
  (.. s toString toLowerCase))

(defn split
  "Splits string on a regular expression.  Optional argument limit is
  the maximum number of splits. Not lazy. Returns vector of the splits."
  {:added "1.2"}
  ([^CharSequence s ^Pattern re]
     (LazilyPersistentVector/createOwning (.split re s)))
  ([ ^CharSequence s ^Pattern re limit]
     (LazilyPersistentVector/createOwning (.split re s limit))))

(defn split-lines
  "Splits s on \\n or \\r\\n."
  {:added "1.2"}
  [^CharSequence s]
  (split s #"\r?\n"))

(defn ^String trim
  "Removes whitespace from both ends of string."
  {:added "1.2"}
  [^CharSequence s]
  (.. s toString trim))

(defn ^String triml
  "Removes whitespace from the left side of string."
  {:added "1.2"}
  [^CharSequence s]
  (loop [index (int 0)]
    (if (= (.length s) index)
      ""
      (if (Character/isWhitespace (.charAt s index))
        (recur (inc index))
        (.. s (subSequence index (.length s)) toString)))))

(defn ^String trimr
  "Removes whitespace from the right side of string."
  {:added "1.2"}
  [^CharSequence s]
  (loop [index (.length s)]
    (if (zero? index)
      ""
      (if (Character/isWhitespace (.charAt s (dec index)))
        (recur (dec index))
        (.. s (subSequence 0 index) toString)))))

(defn ^String trim-newline
  "Removes all trailing newline \\n or return \\r characters from
  string.  Similar to Perl's chomp."
  {:added "1.2"}
  [^CharSequence s]
  (loop [index (.length s)]
    (if (zero? index)
      ""
      (let [ch (.charAt s (dec index))]
        (if (or (= ch \newline) (= ch \return))
          (recur (dec index))
          (.. s (subSequence 0 index) toString))))))

(defn blank?
  "True if s is nil, empty, or contains only whitespace."
  {:added "1.2"}
  [^CharSequence s]
  (if s
    (loop [index (int 0)]
      (if (= (.length s) index)
        true
        (if (Character/isWhitespace (.charAt s index))
          (recur (inc index))
          false)))
    true))

(defn ^String escape
  "Return a new string, using cmap to escape each character ch
   from s as follows:
   
   If (cmap ch) is nil, append ch to the new string.
   If (cmap ch) is non-nil, append (str (cmap ch)) instead."
  {:added "1.2"}
  [^CharSequence s cmap]
  (loop [index (int 0)
         buffer (StringBuilder. (.length s))]
    (if (= (.length s) index)
      (.toString buffer)
      (let [ch (.charAt s index)]
        (if-let [replacement (cmap ch)]
          (.append buffer replacement)
          (.append buffer ch))
        (recur (inc index) buffer)))))