Posts

Showing posts from February 25, 2019

What is the term (if any) for a “pothole”-like cavity in an icy surface such as an ice rink or lake...

Image
0 ...where one might unfortunately catch their skate blade in? Having lived in the southwest part of the country most of my life where there has been neither cause nor occasion for me to experience such a word. How would you caution someone to "lookout for the potholes in the ice!" single-word-requests expressions share | improve this question asked 6 hours ago squidlydeux squidlydeux 1,170 3 8 add a comment  |  ...

Defining a parameterised Fixpoint in Coq

Image
3 I'm trying to define a fixpoint in Coq in which one of the function definitions refers to the other through a parameter, but I'm getting some confusing errors. I've minimised the definition to this: Require Import Coq.Init.Notations. Require Import Coq.Init.Datatypes. Inductive Wrapper (T : Type) := | Wrap : T -> Wrapper T . Inductive Unwrapper := | Empty : Unwrapper | Unwrap : Wrapper Unwrapper -> Unwrapper . Fixpoint Unwrapper_size (u : Unwrapper) {struct u} : nat := match u with | Empty => O | Unwrap w => Wrapper_size w end with Wrapper_size (w : Wrapper Unwrapper) {struct w} : nat := match w with | Wrap _ t => Unwrapper_size t end. which results in this error: Recursive definition of Wrapper_size is ill-formed. In environment Un...