Fix typos as spotted by HUghes
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@ -1,4 +1,4 @@
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\newcommand*{\defeq}{\mathrel{\vcenter{\baselineskip0.5ex \lineskiplimit0pt
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\newcommand{\coloneqq}{\mathrel{\vcenter{\baselineskip0.5ex \lineskiplimit0pt
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\hbox{\scriptsize.}\hbox{\scriptsize.}}}%
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=}
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@ -60,7 +60,7 @@ parts that will be useful in the second part of the project: Showing that
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\section{Problem}
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%
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In the following two subsections I present two examples that illustrate the
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limitaiton inherent in ITT and by extension to the expressiveness of Agda.
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limitation inherent in ITT and by extension to the expressiveness of Agda.
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%
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\subsection{Functional extensionality}
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Consider the functions:
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@ -71,7 +71,7 @@ $f \defeq (n : \bN) \mapsto (0 + n : \bN)$
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$g \defeq (n : \bN) \mapsto (n + 0 : \bN)$
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\end{multicols}
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%
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$n + 0$ is definitionally equal to $n$. We call this \nomen{defnitional
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$n + 0$ is definitionally equal to $n$. We call this \nomen{definitional
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equality} and write $n + 0 = n$ to assert this fact. We call it definitional
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equality because the \emph{equality} arises from the \emph{definition} of $+$
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which is:
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@ -97,7 +97,7 @@ not true.} There is no way to construct a proof asserting the obvious
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equivalence of $f$ and $g$ -- even though we can prove them equal for all
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points. This is exactly the notion of equality of functions that we are
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interested in; that they are equal for all inputs. We call this
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\nomen{pointwise equality}. Where the \emph{points} of a function refers
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\nomen{pointwise equality}, where the \emph{points} of a function refers
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to it's arguments.
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%
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\iffalse
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@ -142,7 +142,7 @@ $$(A \cong B) \cong (A \equiv B)$$
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%
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\subsection{Formalizing Category Theory}
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%
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The above examples serves to illustrate the limitation of Agda. One case where
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The above examples serve to illustrate the limitation of Agda. One case where
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these limitations are particularly prohibitive is in the study of Category
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Theory. At a glance category theory can be described as ``the mathematical study
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of (abstract) algebras of functions'' (\cite{awodey-2006}). So by that token
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@ -157,14 +157,14 @@ typical example of a model is that of sets as models for predicate logic. Thus
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set-theory becomes the meta-theory of the formal language of predicate logic.
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In the context of a given type theory and restricting ourselves to
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\emph{categorical} models a model will consists of mapping `things' from the
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\emph{categorical} models a model will consist of mapping `things' from the
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type-theory (types, terms, contexts, context morphisms) to `things' in the
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meta-theory (objects, morphisms) in such a way that the axioms of the
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type-theory (typing-rules) are validated in the meta-theory. In
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\cite{dybjer-1995} the author describes a way of constructing such models for
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dependent type theory called \emph{Categories with Families} (CwFs).
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In \cite{bezem-2014} the authors device a CwF for Cubical Type Theory. This
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In \cite{bezem-2014} the authors devise a CwF for Cubical Type Theory. This
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project will study and formalize this model. Note that I will \emph{not} aim to
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formalize CTT itself and therefore also not give the formal translation between
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the type theory and the meta-theory. Instead the translation will be accounted
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@ -195,7 +195,7 @@ these as axioms. This approach, however, has other shortcomings, e.g.; you lose
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\nomen{canonicity} (\cite{huber-2016}). Canonicity means that any well-type
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term will (under evaluation) reduce to a \emph{canonical} form. For example for
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an integer $e : \bN$ it will be the case that $e$ is definitionally equal to $n$
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application of $\mathit{suc}$ to $0$ for some $n$; $e = \mathit{suc}^n\ 0$.
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applications of $\mathit{suc}$ to $0$ for some $n$; $e = \mathit{suc}^n\ 0$.
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Without canonicity terms in the language can get ``stuck'' when they are
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evaluated.
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