; $Id: loop.pro,v 1.10 1999/01/22 20:12:17 mgs Stab $
;-------------------------------------------------------------
;+
; NAME:
;        LOOP
;
; PURPOSE:
;        This routine provides a wrapper for function calls that accept
;        only scalars so that they can operate on arrays.
;
; CATEGORY:
;        serious stuff
;
; CALLING SEQUENCE:
;        result = LOOP(name,arg,p1,p2,p3,p4)
;
; INPUTS:
;        NAME --> the name of the function (string)
;
;        ARG --> the argument (array)
;
;        P1 .. P4 --> optional function parameters 
;
; KEYWORD PARAMETERS:
;        unfortunately none. Would be nice if _EXTRA would work.
;
; OUTPUTS:
;        a result *vector* with the same number of elements as arg.
;
; SUBROUTINES:
;
; REQUIREMENTS:
;
; NOTES:
;
; EXAMPLE:
;        a=[0.05,0.01,0.001]
;        print,loop("chisqr_cvf",a,17)
; 
;        IDL prints:
;        27.5871      33.4087      40.7903
;
; MODIFICATION HISTORY:
;        mgs, 05 Dec 1997: VERSION 1.00
;
;-
; Copyright (C) 1997, Martin Schultz, Harvard University
; This software is provided as is without any warranty
; whatsoever. It may be freely used, copied or distributed
; for non-commercial purposes. This copyright notice must be
; kept with any copy of this software. If this software shall
; be used commercially or sold as part of a larger package,
; please contact the author to arrange payment.
; Bugs and comments should be directed to mgs@io.harvard.edu
; with subject "IDL routine loop"
;-------------------------------------------------------------


function loop,name,arg,p1,p2,p3,p4
 
 
   on_error,2   ; return to caller
 
 
   result = fltarr(n_elements(arg))
 
; print,n_elements(p1),n_elements(p2),n_elements(p3),n_elements(p4)
   ; call function with number of parameters supplied
   ; not very elegant but safe.
   ; (would probably look nicer with EXECUTE, but isn't that slower ?)
 
   if (n_elements(p4) gt 0) then begin
       for i=0,n_elements(arg)-1 do   $
           result(i) = call_function(name,arg(i),p1,p2,p3,p4)
       return,result
   endif
 
   if (n_elements(p3) gt 0) then begin
       for i=0,n_elements(arg)-1 do   $
           result(i) = call_function(name,arg(i),p1,p2,p3)
       return,result
   endif
 
   if (n_elements(p2) gt 0) then begin
       for i=0,n_elements(arg)-1 do   $
           result(i) = call_function(name,arg(i),p1,p2)
       return,result
   endif
 
   if (n_elements(p1) gt 0) then begin
       for i=0,n_elements(arg)-1 do   $
           result(i) = call_function(name,arg(i),p1)
       return,result
   endif
 
 
   for i=0,n_elements(arg)-1 do   $
       result(i) = call_function(name,arg(i))
   return,result
 
end