How to modify structure fields inside functions

[Bruno Picasso]

Hi everybody,

I need your help to understand how to modify a structure field inside a function. For example:

>> a.b=3

a =

{

  b =  3

}

>> function modify (s)

> setfield(s,'b',5)

> endfunction

>> modify(a)

ans =

{

  b =  5

}

>> a.b

ans =  3

Thanks for your kind help

Bruno