* PURPOSE
* This type opcode is an auxiliary opcode dedicated to support transformations
* of the type structure. If a type is changed to another type with another
- * opcode the new type will be allocated with new memory. All nodes refereing
+ * opcode the new type will be allocated with new memory. All nodes refering
* to the old type need to be changed to refer the new one. This is simplified
* by turning the old type into an id type that merely forwards to the new type
* that now replaces the old one.
* should automatically check for type_id and eventually follow the forward in
* type_id. Two types are exchanged by a call to exchange_types.
* If a type_id is visible externally report this as bug. If it is assured that
- * this never happens this extern variable can be moved to type_t.h.
+ * this never happens this extern variable can be moved to tpop_t.h.
* NOTES
* This struct is dynamically allocated but constant for the lifetime
* of the library.