Template function to create a read-only active binding.
     
    
    Usage
    read_only_active(private, field, val)
 
     
    
    Arguments
    - private
 
Pointer to the private env of an object
 
- field
 
character(1) the name of the active binding field. It is assumed
that a private field prefixed with a single dot exists, that serves as
storage.
 
- val
 
The value passed to the active binding. If it is not missing,
the function will stop.
 
 
    
    Value
    The value of the active binding-related storage field.