 
Summary: Fixed Points of Type Constructors
and Primitive Recursion (Errata)
Andreas Abel and Ralph Matthes
October 19, 2004
Abstract
Our contribution to CSL 04 [AM04] contains a little error, which is easily corrected by 2 elementary
editing steps (replacing one character and deleting another).
Definition of wellformed contexts (fifth page). Typing contexts should, in contrast to kinding con
texts, only contain type variable declarations without variance information. Hence, the second rule is too
liberal; we must insist on p = . The corrected set of rules is then:
cxt
cxt
, X cxt
cxt A :
, x:A cxt
Definition of welltyped terms (immediately following). Since wellformed typing contexts contain
no variance information, hence = , we might drop the "" in the instantiation rule (fifth rule). The
new set of rules is consequently,
(x:A) cxt
x : A
