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(elisp)Substitution

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Substituting for a Character Code
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   The following functions replace characters within a specified region
based on their character codes.

 - Function: subst-char-in-region start end old-char new-char &optional
          noundo
     This function replaces all occurrences of the character OLD-CHAR
     with the character NEW-CHAR in the region of the current buffer
     defined by START and END.

     If NOUNDO is non-`nil', then `subst-char-in-region' does not
     record the change for undo and does not mark the buffer as
     modified.  This was useful for controlling the old selective
     display feature (Note: Selective Display).

     `subst-char-in-region' does not move point and returns `nil'.

          ---------- Buffer: foo ----------
          This is the contents of the buffer before.
          ---------- Buffer: foo ----------
          
          (subst-char-in-region 1 20 ?i ?X)
               => nil
          
          ---------- Buffer: foo ----------
          ThXs Xs the contents of the buffer before.
          ---------- Buffer: foo ----------

 - Function: translate-region start end table
     This function applies a translation table to the characters in the
     buffer between positions START and END.

     The translation table TABLE is a string; `(aref TABLE OCHAR)'
     gives the translated character corresponding to OCHAR.  If the
     length of TABLE is less than 256, any characters with codes larger
     than the length of TABLE are not altered by the translation.

     The return value of `translate-region' is the number of characters
     that were actually changed by the translation.  This does not
     count characters that were mapped into themselves in the
     translation table.