[Agda] Re: [Coq-Club] Coinductive types and type preservation.

[Thorsten Altenkirch]

Hi,

recently there was a flurry of coinduction on the Coq and Agda lists  
triggered by Nicolas Oury's example that subject reduction fails (a  
fact it seems which was already known by Eduardo Giminez a while ago).  
I talked about this at FP lunch in Nottingham analyzing the problem  
using the concept of boxes - a summary can be found on the fp lunch  
blog (http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=104).

Executive summary: If you restrict the unfolding of recursion you  
should also control the effects of substitution aka local definitions.

Cheers,
Thorsten


This message has been checked for viruses but the contents of an attachment
may still contain software viruses, which could damage your computer system:
you are advised to perform your own checks. Email communications with the
University of Nottingham may be monitored as permitted by UK legislation.