From c73f0c685bcb0de94ee1cc8cf2b050a6b90996f5 Mon Sep 17 00:00:00 2001 From: Robbert Krebbers <mail@robbertkrebbers.nl> Date: Sun, 10 Dec 2017 13:26:11 +0100 Subject: [PATCH] Fix typo in docs: fixpoints can only be taken of endo-functions. --- docs/algebra.tex | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/algebra.tex b/docs/algebra.tex index adf798b09..0a9c8687d 100644 --- a/docs/algebra.tex +++ b/docs/algebra.tex @@ -85,7 +85,7 @@ COFEs are \emph{complete OFEs}, which means that we can take limits of arbitrary The function space $\ofe \nfn \cofeB$ is a COFE if $\cofeB$ is a COFE (\ie the domain $\ofe$ can actually be just an OFE). Completeness is necessary to take fixed-points. -For once, every \emph{contractive function} $f : \ofe \to \cofeB$ where $\cofeB$ is a COFE and inhabited has a \emph{unique} fixed-point $\fix(f)$ such that $\fix(f) = f(\fix(f))$. +For once, every contractive function $f : \cofe \to \cofe$ where $\cofe$ is a COFE and inhabited has a \emph{unique} fixed-point $\fix(f)$ such that $\fix(f) = f(\fix(f))$. This also holds if $f^k$ is contractive for an arbitrary $k$. Furthermore, by America and Rutten's theorem~\cite{America-Rutten:JCSS89,birkedal:metric-space}, every contractive (bi)functor from $\COFEs$ to $\COFEs$ has a unique\footnote{Uniqueness is not proven in Coq.} fixed-point. -- GitLab