[Agda] Strict positivity and indices
Dan Doel
dan.doel at gmail.com
Wed May 9 18:37:15 CEST 2012
Greetings,
There's a recent thread on coq-club about a certain inductive definition here:
https://sympa-roc.inria.fr/wws/arc/coq-club/2012-05/msg00032.html
The Agda equivalent is:
data Val : Set where
nat : ℕ -> Val
vec : (l : List Val) -> 0 < length l -> Val
Coq rejects this as not being strictly positive. Agda doesn't complain.
If I understand the proposed explanation, it's that the second
argument has type 0 < length {Val} l, and the arguments to < are
indices, not parameters (and indices are not strictly positive
positions). So my question is: is Coq right, or is Agda?
-- Dan
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