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elisp: Case Conversion

 
 4.8 Case Conversion in Lisp
 ===========================
 
 The character case functions change the case of single characters or of
 the contents of strings.  The functions normally convert only alphabetic
 characters (the letters ‘A’ through ‘Z’ and ‘a’ through ‘z’, as well as
 non-ASCII letters); other characters are not altered.  You can specify a
 different case conversion mapping by specifying a case table (Case
 Tables).
 
    These functions do not modify the strings that are passed to them as
 arguments.
 
    The examples below use the characters ‘X’ and ‘x’ which have ASCII
 codes 88 and 120 respectively.
 
  -- Function: downcase string-or-char
      This function converts STRING-OR-CHAR, which should be either a
      character or a string, to lower case.
 
      When STRING-OR-CHAR is a string, this function returns a new string
      in which each letter in the argument that is upper case is
      converted to lower case.  When STRING-OR-CHAR is a character, this
      function returns the corresponding lower case character (an
      integer); if the original character is lower case, or is not a
      letter, the return value is equal to the original character.
 
           (downcase "The cat in the hat")
                ⇒ "the cat in the hat"
 
           (downcase ?X)
                ⇒ 120
 
  -- Function: upcase string-or-char
      This function converts STRING-OR-CHAR, which should be either a
      character or a string, to upper case.
 
      When STRING-OR-CHAR is a string, this function returns a new string
      in which each letter in the argument that is lower case is
      converted to upper case.  When STRING-OR-CHAR is a character, this
      function returns the corresponding upper case character (an
      integer); if the original character is upper case, or is not a
      letter, the return value is equal to the original character.
 
           (upcase "The cat in the hat")
                ⇒ "THE CAT IN THE HAT"
 
           (upcase ?x)
                ⇒ 88
 
  -- Function: capitalize string-or-char
      This function capitalizes strings or characters.  If STRING-OR-CHAR
      is a string, the function returns a new string whose contents are a
      copy of STRING-OR-CHAR in which each word has been capitalized.
      This means that the first character of each word is converted to
      upper case, and the rest are converted to lower case.
 
      The definition of a word is any sequence of consecutive characters
      that are assigned to the word constituent syntax class in the
      current syntax table (Syntax Class Table).
 
      When STRING-OR-CHAR is a character, this function does the same
      thing as ‘upcase’.
 
           (capitalize "The cat in the hat")
                ⇒ "The Cat In The Hat"
 
           (capitalize "THE 77TH-HATTED CAT")
                ⇒ "The 77th-Hatted Cat"
 
           (capitalize ?x)
                ⇒ 88
 
  -- Function: upcase-initials string-or-char
      If STRING-OR-CHAR is a string, this function capitalizes the
      initials of the words in STRING-OR-CHAR, without altering any
      letters other than the initials.  It returns a new string whose
      contents are a copy of STRING-OR-CHAR, in which each word has had
      its initial letter converted to upper case.
 
      The definition of a word is any sequence of consecutive characters
      that are assigned to the word constituent syntax class in the
      current syntax table (Syntax Class Table).
 
      When the argument to ‘upcase-initials’ is a character,
      ‘upcase-initials’ has the same result as ‘upcase’.
 
           (upcase-initials "The CAT in the hAt")
                ⇒ "The CAT In The HAt"
 
    Text Comparison, for functions that compare strings; some of
 them ignore case differences, or can optionally ignore case differences.
 

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