repstr.pro

function repstr,obj,in,out
  ;+
  ; NAME:
  ; REPSTR
  ; PURPOSE:
  ; Replace all occurences of one substring by another.
  ; EXPLANATION:
  ; Meant to emulate the string substitution capabilities of text editors
  ; CALLING SEQUENCE:
  ; result = repstr( obj, in, out )
  ;
  ; INPUT PARAMETERS:
  ; obj    = object string for editing, scalar or array
  ; in     = substring of 'obj' to be replaced, scalar
  ;
  ; OPTIONAL INPUT PARMETER:
  ; out    = what 'in' is replaced with, scalar.   If not supplied
  ;   then out = '', i.e. 'in' is not replaced by anything.
  ;
  ; OUTPUT PARAMETERS:
  ; Result returned as function value.  Input object string
  ; not changed unless assignment done in calling program.
  ;
  ; PROCEDURE:
  ; Searches for 'in', splits 'obj' into 3 pieces, reassembles
  ; with 'out' in place of 'in'.  Repeats until all cases done.
  ;
  ; EXAMPLE:
  ; If a = 'I am what I am' then print,repstr(a,'am','was')
  ; will give 'I was what I was'.
  ;
  ; MODIFICATION HISTORY:
  ; Written by Robert S. Hill, ST Systems Corp., 12 April 1989.
  ; Accept vector object strings, W. Landsman   HSTX,   April, 1996
  ; Converted to IDL V5.0   W. Landsman   September 1997
  ;       Convert loop to LONG, vectorize STRLEN call W. Landsman June 2002
  ;       Correct bug in optimization, case where STRLEN(OBJ) EQ
  ;         STRLEN(IN), C. Markwardt, Jan 2003
  ;       Fixed problem when multiple replacements extend the string length
  ;                 D. Finkbeiner, W. Landsman  April 2003
  ;       Allow third parameter to be optional again W. Landsman  August 2003
  ;       Remove limitation of 9999 characters, C. Markwardt Dec 2003
  ;-
  On_error,2
  if N_params() LT 2 then begin
    print,'Syntax - result = REPSTR( obj, in, out )'
    return, obj
  endif

  if N_elements(out) EQ 0 then out = ''
  l1 = strlen(in)
  l2 = strlen(out)
  diflen = l2- l1
  Nstring = N_elements(obj)
  object = obj
  lo = strlen(object) - l1             ;Last character needed to look at
  for i= 0L ,Nstring-1 do begin
    last_pos = 0
    pos = 0
    while ( pos LE lo[i]) and (pos GE 0) do begin
      pos = strpos(object[i],in,last_pos)
      if (pos GE 0) then begin
        first_part = strmid(object[i],0,pos)
        last_part  = strmid(object[i],pos+l1)
        object[i] = first_part + out + last_part
      endif
      last_pos = pos + l2
      lo[i] = lo[i] + diflen           ;Length of string may have changed
    endwhile
  endfor

  return,object

end