pointer to the origin instance of the expression. once a new expression is created, origin is set to 'this'. anytime when an expression copy is created, 'origin' pointer is set to 'origin' pointer value of the original expression.
See Implementation
pointer to the origin instance of the expression. once a new expression is created, origin is set to 'this'. anytime when an expression copy is created, 'origin' pointer is set to 'origin' pointer value of the original expression.