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e562c65774
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e562c65774 | ||
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21328a3d05 |
@ -121,8 +121,8 @@
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\newcommand{\wtypestore}[3]{\ensuremath{#1 = \wtype{#2}{#3}}}
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%\newcommand{\wtype}[2]{\ensuremath{[#1\ #2]}}
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\newcommand{\wtv}[1]{\ensuremath{\tv{#1}_?}}
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%\newcommand{\ntv}[1]{\ensuremath{\underline{\tv{#1}}}}
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\newcommand{\ntv}[1]{\tv{#1}}
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\newcommand{\ntv}[1]{\ensuremath{\underline{\tv{#1}}}}
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%\newcommand{\ntv}[1]{\tv{#1}}
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\newcommand{\wcstore}{\ensuremath{\Delta}}
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%\newcommand{\rwildcard}[1]{\ensuremath{\mathtt{#1}_?}}
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40
unify.tex
40
unify.tex
@ -146,21 +146,28 @@ The \unify{} algorithm internally uses the following data types:
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The algorithm is split into multiple parts:
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\begin{description}
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\item[Step 1:]
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Apply the rules depicted in the figures \ref{fig:normalizing-rules}, \ref{fig:reduce-rules} and \ref{fig:wildcard-rules} exhaustively.
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Starting with the \rulename{circle} rule.
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Apply the rules depicted in the figures \ref{fig:normalizing-rules}, \ref{fig:reduce-rules} and \ref{fig:wildcard-rules} exhaustively,
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starting with the \rulename{circle} rule.
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\item[Step 2:]
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%If there are no $(\type{T} \lessdot \tv{a})$ constraints remaining in the constraint set $C$
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%resume with step 4.
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The rules in figure \ref{fig:step2-rules} offer multiple possibilities to deal with constraints of the form $\type{N} \lessdot \tv{a}$.
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This builds a search tree over multiple possible solutions.
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\unify{} has to try each branch and accumulate the resulting solutions into a solution set.
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The second step is nondeterministic.
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%\unify{} has to pick the right transformation for each constraint of the form $\type{N} \lessdot \tv{a}$.
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%The rules in figure \ref{fig:step2-rules} offer three possibilities to deal with constraints $\type{N} \lessdot \tv{a}$.
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For every $\type{T} \lessdot \tv{a}$ constraint \unify{} has to pick exactly one transformation from figure \ref{fig:step2-rules}.
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The same principle goes for constraints of the form $\tv{a} \lessdot \type{N}, \tv{a} \lessdot \tv{b}$ and the two transformations in figure \ref{fig:step2-rules2}.
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%They have to be applied until the constraint set holds no constraints of the form $\tv{a} \lessdot \type{N}, \tv{a} \lessdot \tv{b}$.
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If atleast one transformation was applied in this step revert to step 1.
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Otherwise proceed with step 3.
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%This builds a search tree over multiple possible solutions.
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%\unify{} has to try each branch and accumulate the resulting solutions into a solution set.
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$\type{T} \lessdot \ntv{a}$ constraints have three and $\type{T} \lessdot \wtv{a}$ constraints have five possible transformations.
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%$\type{T} \lessdot \ntv{a}$ constraints have three and $\type{T} \lessdot \wtv{a}$ constraints have five possible transformations.
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\item[Step 3:]
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We apply the rules in figure \ref{fig:cleanup-rules} exhaustively and proceed with step 4.
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Apply the rules in figure \ref{fig:cleanup-rules} exhaustively and move on with step 4.
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\item[Step 4:] \textit{(Generating Result)}
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Apply the rules in figure \ref{fig:generation-rules} until $\wildcardEnv = \emptyset$ and $C = \emptyset$.
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@ -263,6 +270,12 @@ To only rename the respective wildcards the reduce rule renames wildcards up to
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\item[Free Variables:]
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The $\text{fv}$ function assumes every wildcard type variable to be a free variable aswell.
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% TODO: describe a function which determines free variables? or do an example?
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\begin{align*}
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\text{fv}(\rwildcard{A}) &= \set{ \rwildcard{A} } \\
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\text{fv}(\ntv{a}) &= \emptyset \\
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\text{fv}(\wtv{a}) &= \set{\wtv{a}} \\
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\text{fv}(\wctype{\Delta}{C}{\ol{T}}) &= \set{\text{fv}(\type{T}) \mid \type{T} \in \ol{T}} / \text{dom}(\Delta) \\
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\end{align*}
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\item[Fresh Wildcards:]
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$\text{fresh}\ \overline{\wildcard{A}{\tv{u}}{\tv{l}}}$ generates fresh wildcards.
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@ -445,11 +458,11 @@ $
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\hline
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\vspace*{-0.4cm}\\
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\wildcardEnv \vdash C
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\end{array}
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\end{array}
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$
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\\\\
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\quad
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\rulename{Pit}
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& $
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$
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\begin{array}[c]{l}
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\wildcardEnv \vdash C \cup \set{ \tv{a} \lessdot_1 \bot } \\
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\hline
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@ -530,10 +543,7 @@ $
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\vspace*{-0.4cm}\\
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\wildcardEnv \vdash C
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\end{array}
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$
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\\\\
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\rulename{Erase}
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& $
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\quad
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\begin{array}[c]{l}
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\wildcardEnv \vdash C \cup \, \set{ \type{T} \lessdot \type{T} } \\
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\hline
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@ -970,7 +980,7 @@ $\set{\tv{a} \doteq \type{N}} \in C$ with $\text{fv}(\type{N}) \cap \Delta_{in}
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}
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\end{center}
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\caption{Step 2 branching: Multiple rules can be applied to the same constraint}
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\label{fig:step2-rules}
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\label{fig:step2-rules2}
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\end{figure}
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\begin{figure}
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