Removing elements from structures

[Etienne Grossmann]

From: Roberto Hernandez <address@hidden>

# Hi all,

  Hello

# I've been looking through the documentation, but can't find how to 
# remove an element from a structure.

# Suppose I define the following:

# a.name = "Bob"
# a.lastname = "Hope"
# a.phone = "555-5555"

  I wrote a function rmfield () for that purpose.

octave:7> a = rmfield (a, "phone") 
a =
{
  name = Bob
  lastname = Hope
}

# TIA,

  You're welcome, if that's what you needed. Note however that the
method is not very efficient : it creates a new hash and copies
everything except the unwanted elements. See yourself :

======================================================================
##        t = rmfield(s,key1,...)
## 
## Removes key1, key2, ...  from structure s. 
## Return s if s is not a struct. Any better behavior?
## 
## For m****b compatibility and flexibility. 
##
## Basically, does a 'filtering' copy of s.
##
## See also cmpstruct, fields, setfield, isstruct, getfield, isfield,
## catstruct and struct. 
##

## Author:        Etienne Grossmann  <address@hidden>
## Last modified: January 2000

function t = rmfield(s,...)
if ! is_struct(s) ,                     
  t = s ;
  return
end
va_start() ; 
rmf = ' ' ;
nargin-- ;
while nargin-- ,
  tmp = va_arg() ;
  if ! isstr(tmp) ,
    printf('struct: called with non-string key\n') ; 
    tmp
    keyboard
  else
    rmf = [rmf,tmp,' '] ;
  end
end
for [val, key] = s ,
  if ! index(rmf,[' ',key,' ']) ,       % Check if key is wanted
    eval(['t.',key,'=val;']) ;          % Copy
  end
end
======================================================================

  This could easily be improved upon, but I just wanted something that
worked. That and other struct tools can be found at 

   http://www.isr.ist.utl.pt/~etienne/octave/

  Hey! Even better, you can find it at Octave-forge (thanks Paul, for
putting it in)

  http://octave.sf.net

  Cheers,

  Etienne

-- 
Etienne Grossmann ------ http://www.isr.ist.utl.pt/~etienne



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