diff --git a/dp.tex b/dp.tex index e2e8447c707aa8423ced2e288ff5ee0e22a96b7c..ae9276f5ea75b6cb75e0e92e74d0917661fc598d 100644 --- a/dp.tex +++ b/dp.tex @@ -1,13 +1,100 @@ -\section{Dependency pairs} +\section{Fully applied signature symbol and structural order} \begin{defi}[Order associated to accessible subterms] We define $\surterm_{acc}$ as the transitive closure of $\paren{f\,t_1\dots t_{\arity(c)}}\surterm_{acc}(t_i\,\bar u)$, - where $f\in\CObj$, $\tau(f)=\Pi\overline{(x:T)}.V$, $i\in\Acc(f)$, $T_i=\Pi\overline{(x:U)}.W$ - and $\overline{\crochet{\sur{u}{x}}}\vDash\overline{(x:U)}$. + where $f\in\CObj$, $\tau(f)=\Pi\overline{(x:T)}.U$, + $i\in\Acc(f)$, $T_i=\Pi\overline{(y:V)}.W$ + and $\overline{\crochet{\sur{u}{y}}}\vDash\overline{(y:V)}$. +\end{defi} + +\begin{defi}[Function applied to reducible terms] + Let + \[ + \mbb{U}=\enscond{f\,\bar t}{ + \begin{matrix} + \vdash\tau(f):s(f),\\ + \tau(f)\in\interp{s(f)},\\ + \tau(f)=\Pi\overline{(x:T)}. T',\\ + T'\text{ is not an arrow}\\ + \valabs{\bar t}=\arity(f)\\ + \crochet{\overline{\sur{t}{x}}}\vDash\overline{(x:T)} + \end{matrix} + } + \] \end{defi} +\begin{defi}[$\rew_{arg}$] + Let $f\,\bar t\in\mbb{U}$. + $f\,\bar t\rew_{arg}u$ if $u=f\,\bar t'$, there is a $i$ such that $t_i\rew t'_i$ + and for all $j\neq i$, $t_j=t'_j$. +\end{defi} + +\begin{lem}\label{lem-subacc-wf} + There is no infinite sequence $(t_i)_{i\in\N}$ such that $t_0\in\mbb{U}$ and for all $i\in\N$, $t_i\surterm_{acc}t_{i+1}$. +\end{lem} +\begin{proof} + Let us assume that there is such an infinite sequence. + + First note that every $t_i$ is headed by an element of $\CObj$, otherwise there is no $t$ such that $t_i\surterm_{acc}t$. + + Hence, among every infinite sequence, + let us choose one such that $t_0=f\,\bar u$ + where $\tau(f)=\Pi\overline{(x:T)}.C\,\bar v$ + and for all $C'\prec C$, there is no infinite sequence starting by a constructor of $C'$. + + We will prove that for every $i$, $t_i=t'_i\,\bar v$ + where $t'_0=t_0$, for all $i$, $t'_i\surterm t'_{i+1}$ and $t'_i$ is headed by a constructor of a type equivalent to $C$. + + Let $i$ be such that $t_i$ has this property. + Hence $t_i=t'_i\,\bar v$. + Since $t_i$ is headed by a constructor, + $t'_i$ too, $t'_i=c\,\bar u$. + Since $t'_i\,\bar v\surterm_{acc}t_{i+1}$, two options: + \begin{itemize} + \item + if $t_{i+1}=u_j\,\bar x$, then $u_j\subterm t'_{i}$ hence there is a $t'_{i+1}$ (namely $u_j$) such that $t_{i+1}=t'_{i+1}\,\bar x$ such that $t'_i\surterm t'_{i+1}$. + By definition of accessibility, if $\tau(c)=\Pi\overline{(x:T)}.C'\,\bar w$ with $C'\sim C$, + $T_j\in\Froz_{\g\bar m$ if there is a rule $f\bar l\rul r\in\mcal{R}$, @@ -149,28 +236,6 @@ \end{itemize} \end{defi} -\begin{defi}[Function applied to reducible terms] - Let - \[ - \mbb{U}=\enscond{f\,\bar t}{ - \begin{matrix} - \vdash\tau(f):s(f),\\ - \tau(f)\in\interp{s(f)},\\ - \tau(f)=\Pi\overline{(x:T)}. T',\\ - T'\text{ is not an arrow}\\ - \valabs{\bar t}=\arity(f)\\ - \crochet{\overline{\sur{t}{x}}}\vDash\overline{(x:T)} - \end{matrix} - } - \] -\end{defi} - -\begin{defi}[$\rew_{arg}$] - Let $f\,\bar t\in\mbb{U}$. - $f\,\bar t\rew_{arg}u$ if $u=f\,\bar t'$, there is a $i$ such that $t_i\rew t'_i$ - and for all $j\neq i$, $t_j=t'_j$. -\end{defi} - \begin{lem}[Pseudo-adequacy]\label{lem-pseudo-adequacy} For all $f\,\bar l$, $\G$, $u$ and $U$, if $\G\vdash_{f\bar l} u:U$, $\sg\vDash\G$ and for all $g\sqsubset f$, $g\in\interp{\tau(g)\sg}$, @@ -190,54 +255,12 @@ Hence, $g\sqsubseteq h$. Furthermore, by \indlem{lem-order-typ}, $h\sqsubset f$ because $\G\vdash_{\sqsubset f}\tau(g):s(g)$. Hence by transitivity, $g\sqsubset f$. - + We then have $g\in\interp{\tau(g)\sg}$ by hypothesis. \qedhere \end{description} \end{proof} - -\begin{lem}\label{lem-subacc-wf} - Let $f\,\bar u\in\mbb{U}$. - There is no infinite sequence $(t_i)_{i\in\N}$ such that $t_0=f\,\bar u$ and for all $i\in\N$, $t_i\surterm_{acc}t_{i+1}$. -\end{lem} -\begin{proof} - \begin{itemize} - \item - If $f\notin\CObj$, then there is no $t$ such that $f\,\bar u\surterm_{acc}t$. - \item - So, let us consider $f\in\CObj$. - Then $\tau(f)=\Pi\overline{(x:T)}.C\,\bar v$. - - By induction on $\succ$, - let's assume that for all $C'\prec C$, - for all terms headed by a constructor of $C'$, - there is no infinite sequence with the expected property. - - There is a $i\in\Acc(f)$ such that $t_1=u_i\,\bar w$. - By definition of accessibility, $T_i\in\Froz_{\