The sort of the bound variable.
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      (Since version ) see corresponding Javadoc for more information.
Common trait for
IExpressionclasses that bind variables. Bound variables are represented using de Bruijn indexes.