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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).
De nition of wellformed contexts ( fth 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 = Æ. The corrected set of rules is then:
cxt
cxt
; X Æ cxt
cxt ` A :
; x : A cxt
De nition of welltyped terms (immediately following). Since wellformed typing contexts contain
no variance information, hence Æ = , we might drop the \Æ" in the instantiation rule ( fth rule). The
new set of rules is consequently,
(x : A) 2 cxt
` x : A
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