GNU Info

(elisp)Case Conversion

---

Next: Case Tables Prev: Formatting Strings Up: Strings and Characters

---

Enter node , (file) or (file)node

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 (Note: 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 a character or a string to lower case.

     When the argument to `downcase' is a string, the function creates
     and returns a new string in which each letter in the argument that
     is upper case is converted to lower case.  When the argument to
     `downcase' is a character, `downcase' returns the corresponding
     lower case character.  This value is an integer.  If the original
     character is lower case, or is not a letter, then the value equals
     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 a character or a string to upper case.

     When the argument to `upcase' is a string, the function creates
     and returns a new string in which each letter in the argument that
     is lower case is converted to upper case.

     When the argument to `upcase' is a character, `upcase' returns the
     corresponding upper case character.  This value is an integer.  If
     the original character is upper case, or is not a letter, then the
     value returned equals 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 creates and 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 (Note: Syntax Class Table).

     When the argument to `capitalize' is a character, `capitalize' has
     the same result 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
     This function capitalizes the initials of the words in STRING,
     without altering any letters other than the initials.  It returns
     a new string whose contents are a copy of STRING, 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 (Note: Syntax Class Table).

          (upcase-initials "The CAT in the hAt")
               => "The CAT In The HAt"

   Note: Text Comparison, for functions that compare strings; some of
them ignore case differences, or can optionally ignore case differences.