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clojure.string

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
   thread-safety is your responsibility.

Provides most standard string manipulation and processing function that you'd expect in any general-purpose programming language.

In Clojure and ClojureScript strings are represented using the native platform implementation, and can be directly manipulated, e.g. (.toLowerCase "FOO") ;=> "foo". The clojure.string namespace gives you the ability to manipulate strings in an idiomatic way: (clojure.string/lower-case "FOO") ;=> "foo".

Something to keep in mind is most (all?) of these functions take the string to act on as the first parameter, lending themselves well for use with the single-thrush operator (->) , as in this contrived example:

(require '[clojure.string :as str])

(-> "  .LIRpa   ni  yAD    dloc thgIrb  a sAw Ti  "
    str/reverse
    str/trim
    str/lower-case
    (str/replace #"\s+" " ")
    str/capitalize)

;;=> "It was a bright cold day in april"
Vars in clojure.string

b

blank?
True if s is nil, empty, or contains only whitespace.

c

capitalize
Converts first character of the string to upper-case, all other characters to lower-case.

e

ends-with?
True if s ends with substr.
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.

i

includes?
True if s includes substr.
index-of
Return index of value (string or char) in s, optionally searching forward from from-index or nil if not found.

j

join
Returns a string of all elements in coll, as returned by (seq coll), separated by an optional separator.

l

last-index-of
Return last index of value (string or char) in s, optionally searching backward from from-index or nil if not found.
lower-case
Converts string to all lower-case.

r

re-quote-replacement
Given a replacement string that you wish to be a literal replacement for a pattern match in replace or replace-first, do the necessary escaping of special characters in the replacement.
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. The replacement is literal (i.e. none of its characters are treated specially) for all cases above except pattern / string. For pattern / string, $1, $2, etc. in the replacement string are substituted with the string that matched the corresponding parenthesized group in the pattern. If you wish your replacement string r to be used literally, use (re-quote-replacement r) as the replacement argument. See also documentation for java.util.regex.Matcher's appendReplacement method. Example: (clojure.string/replace "Almost Pig Latin" #"\b(\w)(\w+)\b" "$2$1ay") -> "lmostAay igPay atinLay"
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. The replacement is literal (i.e. none of its characters are treated specially) for all cases above except pattern / string. For pattern / string, $1, $2, etc. in the replacement string are substituted with the string that matched the corresponding parenthesized group in the pattern. If you wish your replacement string r to be used literally, use (re-quote-replacement r) as the replacement argument. See also documentation for java.util.regex.Matcher's appendReplacement method. Example: (clojure.string/replace-first "swap first two words" #"(\w+)(\s+)(\w+)" "$3$2$1") -> "first swap two words"
reverse
Returns s with its characters reversed.

s

split
Splits string on a regular expression. Optional argument limit is the maximum number of splits. Not lazy. Returns vector of the splits.
split-lines
Splits s on \n or \r\n.
starts-with?
True if s starts with substr.

t

trim
Removes whitespace from both ends of string.
trim-newline
Removes all trailing newline \n or return \r characters from string. Similar to Perl's chomp.
triml
Removes whitespace from the left side of string.
trimr
Removes whitespace from the right side of string.

u

upper-case
Converts string to all upper-case.