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Corrections in doc #177

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2 changes: 1 addition & 1 deletion doc/Gamma0-chapter.tex
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
\chapter{The Ordinal \texorpdfstring{$\Gamma_0$}{Gamma0} (first draft)}

\label{chap:gamma0}

\emph{This chapter and the files it presents are still very incomplete, considering the impressive properties of $\Gamma_0$~\cite{Gallier91}. We hope to add new material soon, and accept contributions!}

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33 changes: 17 additions & 16 deletions doc/epsilon0-chapter.tex
Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,8 @@
\label{cnf-math-def}
\label{chap:T1}

In this chapter, we adapt to \coq{} the well-known~\cite{KP82} proof that Hercules eventually wins every battle, whichever the strategy of each player.
In other words, we present a formal and self contained proof of termination of all [free] hydra battles.
In this chapter, we adapt to \coq{} the well-known proof~\cite{KP82} that Hercules eventually wins every battle, whichever the strategy of each player.
In other words, we present a formal and self-contained proof of termination of all [free] hydra battles.
First, we take from Manolios and Vroon~\cite{Manolios2005} a representation of the ordinal $\epsilon_0$ as terms in Cantor normal form. Then, we define a variant for hydra battles as a measure that maps any hydra to some ordinal strictly less than $\epsilon_0$.


Expand All @@ -16,7 +16,7 @@ \section{The ordinal \texorpdfstring{\(\epsilon_0\)}{epsilon0}}

The ordinal \(\epsilon_0\) is the least ordinal number that satisfies
the equation \(\alpha = \omega^\alpha\), where \(\omega\) is
the least infinite ordinal.
the least infinite ordinal\footnote{For a precise ---\,\emph{i.e.} mathematical\,--- definition of $\omega^\alpha$, please see Sect.~\vref{sect:AP-and-phi0}.} .
Thus, we can intuitively consider \(\epsilon_0\) as an
\emph{infinite} \(\omega\)-tower.

Expand All @@ -28,10 +28,10 @@ \subsection{Cantor normal form}

Any ordinal strictly less that \(\epsilon_0\)
can be finitely represented by a unique \emph{Cantor normal form},
that is, an expression which is either the ordinal \(0\) or
that is, an expression which is
a sum \(\omega^{\alpha_1} \times n_1 + \omega^{\alpha_2} \times n_2 +
\dots + \omega^{\alpha_p} \times n_p\) where all the \(\alpha_i\)
are ordinals in Cantor normal form, \(\alpha_1 > \alpha_2 > \alpha_p\),
\dots + \omega^{\alpha_p} \times n_p\) where $p\in\mathbb{N}$, all the \(\alpha_i\)
are ordinals in Cantor normal form, \(\alpha_1 > \alpha_2 > \alpha_p\)
and all the \(n_i\) are positive integers.

An example of Cantor normal form is displayed in Fig \ref{fig:cnf-example}:
Expand All @@ -55,8 +55,7 @@ \subsection{Cantor normal form}
to this type, and finally prove that our representation fits well with
the expected mathematical properties: the order we define is a well order,
and the decomposition into Cantor normal form is consistent
with the implementation of the arithmetic operations of exponentiation of base \(\omega\)
and addition.
with usual definition of ordinals, for instance in \gaia~\cite{Gaia}, Schütte's book~\cite{schutte}, or larger ordinal notations~\vref{chap:gamma0}.

\paragraph*{Remark}
\label{sec:orgheadline65}
Expand Down Expand Up @@ -131,7 +130,7 @@ \subsubsection{Example}
\paragraph{Remark}
For simplicity's sake, we chose to forbid expressions of the form $\omega^\alpha\times 0 + \beta$. Thus, the construction (\texttt{cons $\alpha$ $n$ $\beta$}) is intended to represent the
ordinal $\omega^\alpha\times(n+1)+\beta$ and not $\omega^\alpha\times n+\beta$.
In a future version, we should replace the type \texttt{nat} with \texttt{positive} in \texttt{T1}'s
In a future version, we would like to replace the type \texttt{nat} with standard library's type \texttt{positive} in \texttt{T1}'s
definition. But this replacement would take a lot of time \dots{}


Expand Down Expand Up @@ -210,11 +209,11 @@ \subsubsection{The ordinal \(\omega\)}

\input{movies/snippets/T1/omegaDef}

Note that \texttt{omega} is not an identifier in \HydrasLib, thus any tactic like \texttt{unfold omega} would fail.
Note that \texttt{T1omega} is not an identifier in \HydrasLib, thus any tactic like \texttt{unfold T1omega} would fail.

\index{gaiabridge}{The ordinal $\omega$}
\paragraph*{\gaiasign}
In \texttt{gaia.ssete9}, the ordinal $\omega$ is bound to the \emph{constant} \texttt{T1omega}.
In \texttt{gaia.ssete9}, the ordinal $\omega$ is bound to the \emph{constant} \texttt{T1omega} (not a notation).



Expand Down Expand Up @@ -292,7 +291,7 @@ \subsection{Pretty-printing ordinals in Cantor normal form}

\index{hydras}{Projects}
\begin{project}
Design (in \ocaml?) a set of tools for systematically pretty printing ordinal terms in Cantor normal form.
Design tools for systematically pretty printing ordinal terms in Cantor normal form.
\end{project}


Expand All @@ -315,6 +314,8 @@ \subsection{Comparison between ordinal terms}

\input{movies/snippets/T1/compareDef}

\input{movies/snippets/T1/Instances}


\label{Predicates:lt-T1}
Please note that this definition of \texttt{lt} makes it easy to write proofs by computation, as shown by the following examples.
Expand All @@ -325,11 +326,11 @@ \subsection{Comparison between ordinal terms}
\input{movies/snippets/T1/ltExamples}


Links between the function \texttt{compare} and the relations
\texttt{lt} and \texttt{eq} are established through the following lemmas (~\vref{sect:comparable-def}).
\vspace{4pt}
% Links between the function \texttt{compare} and the relations
% \texttt{lt} and \texttt{eq} are established through the following lemmas (~\vref{sect:comparable-def}).
% \vspace{4pt}


\input{movies/snippets/T1/Instances}

\paragraph*{\gaiasign}
\index{gaiabridge}{Strict order on ordinals below $\epsilon_0$}
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18 changes: 8 additions & 10 deletions doc/gaia-chapter.tex
Original file line number Diff line number Diff line change
Expand Up @@ -121,21 +121,19 @@ \subsubsection{Refinements: Definitions}


Functions \texttt{h2g} and \texttt{g2h} allow us to define
a notion of ``data-refinement'' for constants, functions, predicates and relations. The following definitions express that some
a notion of ``data-refinement'' for constants, functions, predicates and relations. The following definitions express that a given
constant, function, relation defined in \HydrasLib ``implements'' the same concept of \gaia.







From~\href{../theories/html/gaia_hydras/T1Bridge.html}%
{\texttt{gaia\_hydras.T1Bridge}}.

\inputsnippets{T1Bridge/refineDefs}

Refinement lemmas can be easily ``reversed''.

\inputsnippets{T1Bridge/refines1R, T1Bridge/refines2R}
\inputsnippets{T1Bridge/refines1R}

\inputsnippets{T1Bridge/refines2R}

\subsection{Examples of refinement}
Both of our libraries define constants like $0$, $1$, $\omega$, and arithmetic functions: successor, addition, multiplication, and exponential of base $\omega$ (function $\phi_0$). We prove that these definitions are mutually consistent. Finally, we prove that the boolean predicates `` to be in normal form'' are equivalent.
Expand Down Expand Up @@ -202,10 +200,10 @@ \subsection{Looking for a lemma}
$\alpha \times \beta=\beta$.

The following command lists us `gaia's lemmas (thanks to
\gaia's \texttt{cantor\_scope}.
\gaia's \texttt{cantor\_scope}).
\inputsnippets{T1Bridge/SearchDemoa}

With \texttt{t1\_scope}:
Within \texttt{t1\_scope}:
\inputsnippets{T1Bridge/SearchDemob}

\section{Importing Definitions and theorems from \HydrasLib}
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14 changes: 7 additions & 7 deletions doc/hydras.tex
Original file line number Diff line number Diff line change
Expand Up @@ -556,15 +556,15 @@ \part{Hydras and ordinals}
\include{Gamma0-chapter}


\part{Ackermann, G\"{o}del, Peano\,\dots}
%\part{Ackermann, G\"{o}del, Peano\,\dots}

\include{chap-intro-goedel}
%\include{chap-intro-goedel}
\include{chapter-primrec}
\include{chapter-fol}
\include{chapter-natural-deduction}
\include{chapter-lnn-lnt}
\include{chapter-encoding}
\include{chapter-expressible}
% \include{chapter-fol}
% \include{chapter-natural-deduction}
% \include{chapter-lnn-lnt}
% \include{chapter-encoding}
% \include{chapter-expressible}


\part{A few certified algorithms}
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2 changes: 2 additions & 0 deletions doc/schutte-chapter.tex
Original file line number Diff line number Diff line change
Expand Up @@ -419,6 +419,7 @@ \subsubsection{Multiplication by a natural number}
\input{movies/snippets/Addition/multFin}

\section{The exponential of basis \texorpdfstring{$\omega$}{omega}}
\label{sect:AP-and-phi0}

In this section, we define the function which maps any $\alpha\in\mathbb{O}$ to
the ordinal $\omega^\alpha$, also written
Expand Down Expand Up @@ -446,6 +447,7 @@ \subsection{Additive principal ordinals}

\subsection{The function \texttt{phi0}}


Let us call $\phi_0$ the ordering function of \texttt{AP}.
In the mathematical text, we shall use indifferently the notations $\omega^\alpha$ and $\phi_0(\alpha)$.

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2 changes: 1 addition & 1 deletion theories/ordinals/Epsilon0/T1.v
Original file line number Diff line number Diff line change
Expand Up @@ -543,7 +543,7 @@ Fixpoint nf_b (alpha : T1) : bool :=
(nf_b a && nf_b b && (bool_decide (lt a' a)))%bool
end.

Definition nf alpha :Prop := nf_b alpha.
Definition nf alpha :Prop := nf_b alpha.
(* end snippet nfDef *)

(* begin snippet badTerm *)
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