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2020.Extensional equality preservation and verified generic programming/About.lidr
View file @ b4e5227f
......@@ -106,7 +106,7 @@ The proof uses pattern matching, which is straightforward here because
%endif
%
In a similar way, one can prove that |(=)| is an equivalence relation:
Reflexivity is directly implemented by |Refl|, while symmetry and
reflexivity is directly implemented by |Refl|, while symmetry and
transitivity can be proven by pattern matching.
......@@ -160,9 +160,10 @@ but not the converse, normally referred to as \emph{function extensionality}:
When working with functions, extensional equality is often the notion of
interest and libraries of formalized mathematics typically provide
definitions like |<=>| and basic results like |IEqImplEE|, see for
example |homot| and |eqtohomot| in Part A of the UniMath library \citep{UniMath}
or |eqfun| in Coq \citep{CoqProofAssistant}.
definitions like |<=>| and basic results like |IEqImplEE|.
%
See for example |homot| and |eqtohomot| in Part A of the UniMath
library \citep{UniMath} or |eqfun| in Coq \citep{CoqProofAssistant}.
In reasoning about generic programs in the style of the Algebra of
Programming \citep{DBLP:books/daglib/0096998,mu2009algebra} and, more
......@@ -200,7 +201,7 @@ two-argument version of extensional equality preservation:
> compPresEE : {A, B, C : Type} -> {g, g' : B -> C} -> {f, f' : A -> B} ->
> g <=> g' -> f <=> f' -> g . f <=> g' . f'
> compPresEE {g} {g'} {f} {f'} gExtEq fExtEq x =
> compPresEE {g} {g'} {f} {f'} gExtEq {-"\ "-} fExtEq {-"\ "-} x =
> ( (g . f) x ) ={ Refl }=
> ( g (f x) ) ={ cong (fExtEq x) }=
> ( g (f' x) ) ={ gExtEq (f' x) }=
......@@ -209,8 +210,8 @@ two-argument version of extensional equality preservation:
The right hand side is a chain of equal expressions connected by the
|={| proofs |}=| of the individual steps within special braces and
ending in |QED|, see ``Preorder reasoning'' in
\citep{idrisdocs}.
ending in |QED|, see ``Preorder reasoning'' in the documentation by
\citet{idrisdocs}.
%
The steps with |Refl| are just for human readability, they could be
omitted as far as Idris is concerned.
......@@ -243,10 +244,10 @@ This paper is also about ADTs and generic programming.
%
More specifically, we show how to exploit the notion of extensional
equality preservation to inform the design of ADTs for generic
programming and embedded domain-specific languages (DSL).
programming and embedded domain-specific languages (DSLs).
%
This is exemplified in sections \ref{section:functors} and
\ref{section:monads} for ADTs for functors and monads but we conjecture
\ref{section:monads} with ADTs for functors and monads but we conjecture
that other abstract data types, e.g. for applicatives and arrows, could
also profit from a design informed by the notion of preservation of
extensional equality.
......@@ -285,8 +286,8 @@ of important research for the last thirty years.
Since Hofmann's seminal work \citep{hofmann1995extensional}, setoids
have been the established, but also often dreaded (who coined the
expression \emph{``setoid hell''}?) means to deal with extensional
concepts in intensional type theory, see also section
\ref{section:relatedwork}.
concepts in intensional type theory (see also section
\ref{section:relatedwork}).
%
Eventually, the study of Martin-Löf's equality type has lead to the
development of Homotopy Type Theory and Voevodsky's Univalent
......@@ -326,11 +327,11 @@ These can be type-checked with Idris 1.3.2 and are available at
%, see \texttt{README.md} in the paper's folder.
%
In the next section we present a motivating example from monadic
dynamical systems, in section~\ref{section:functors} we explore
extensional equality preservation for functors and in section
\ref{section:monads} for monads.
%
We continue with dynamical systems applications in section~\ref{section:applications}
and finish with related work (section~\ref{section:relatedwork}) and
conclusions (section~\ref{section:conclusions}).
% In the next section we present a motivating example from monadic
% dynamical systems, in section~\ref{section:functors} we explore
% extensional equality preservation for functors and in section
% \ref{section:monads} for monads.
% %
% We continue with dynamical systems applications in section~\ref{section:applications}
% and finish with related work (section~\ref{section:relatedwork}) and
% conclusions (section~\ref{section:conclusions}).
2020.Extensional equality preservation and verified generic programming/Applications.lidr
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......@@ -141,6 +141,7 @@ As for |flowLemma2|, proving the representation lemma is straightforward
but crucially relies on associativity of Kleisli composition and thus, as
seen in section \ref{section:monads}, on preservation of extensional
equality:
\pagebreak
% > reprLemma f Z mx =
% > ( (repr (flow f Z)) mx ) ={ Refl }=
......@@ -150,7 +151,7 @@ equality:
% > ( flowDet (repr f) Z mx ) QED
> reprLemma f Z mx = Fat.pureRightIdKleisli id mx
>
> reprLemma f (S m) mx =
> ( repr (flow f (S m)) mx ) ={ Refl }=
> ( (id >=> flow f (S m)) mx ) ={ Refl }=
......@@ -166,11 +167,11 @@ Notice also the application of |kleisliLeapfrog| to deduce |(id >=>
flow f m) ((id >=> f) mx)| from |((id >=> f) >=> flow f m) mx|.
%
If we had formulated the theory in terms of bind instead of Kleisli
composition, the two expressions would be intensionally equal.
composition, the two expressions would have been intensionally equal.
\paragraph*{Flows and trajectories.}
%
The last application of preservation of extensional
Our last application of preservation of extensional
equality in the context of dynamical systems theory is a result about
flows and trajectories.
%
......@@ -188,7 +189,7 @@ is an |M|-structure containing just |[x]|.
To compute the trajectories for |S n| steps, we first bind the outcome
of a single step |f x : M X| into |trj f n|.
%
This results in an |M|-structure of vectors of length |S n|.
This results in an |M|-structure of vectors of length |n|.
%
Finally, we prepend these possible trajectories with the initial state
|x|.
......@@ -284,4 +285,4 @@ induction.
%
As in the |flowTrjLemma| discussed above, |map| preserving extensional
equality turns out to be pivotal in applying the induction hypothesis,
see \citep{brede2020} for details.
see \citet{brede2020} for details.
2020.Extensional equality preservation and verified generic programming/Conclusions.lidr
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......@@ -12,7 +12,7 @@
\label{section:conclusions}
In dependently typed programming in the context of Martin-Löf type
theories \citep{nordstrom1990programming, martinlof1984}, the problem of
theories \citep{martinlof1984, nordstrom1990programming}, the problem of
how to specify abstract data types for verified generic programming is
still not well understood.
%
......
2020.Extensional equality preservation and verified generic programming/Example.lidr
View file @ b4e5227f
......@@ -86,8 +86,7 @@ The base case is trivial
For readability, we spell out the proof sketch for the induction step in
full:
> flowLemma f ( S n) =
> ( flowL f (S n) ) ={ Refl }=
> flowLemma f ( S n) = ( flowL f (S n) ) ={ Refl }=
> ( flowL f n . f ) ={ compPresIE (flowLemma f n) Refl }=
> ( flowR f n . f ) ={ flowRLemma f n }=
> ( f . flowR f n ) ={ Refl }=
......@@ -110,14 +109,21 @@ associativity and preservation of intensional equality again.
< flowRLemma : {X : Type} -> (f : X -> X) -> (n : Nat) -> flowR f n . f = f . flowR f n
> flowRLemma f Z = Refl
> flowRLemma f ( S n) =
> ( flowR f (S n) . f ) ={ Refl }=
> flowRLemma f ( S n) = ( flowR f (S n) . f ) ={ Refl }=
> ( (f . flowR f n) . f ) ={ compAssociative f (flowR f n) f }=
> ( f . (flowR f n . f) ) ={ compPresIE Refl (flowRLemma f n) }=
> ( f . (f . flowR f n) ) ={ Refl }=
> ( f . flowR f (S n) ) QED
\end{joincode}
% > flowRLemma f Z = Refl
% > flowRLemma f ( S n) =
% > ( flowR f (S n) . f ) ={ Refl }=
% > ( (f . flowR f n) . f ) ={ compAssociative f (flowR f n) f }=
% > ( f . (flowR f n . f) ) ={ compPresIE Refl (flowRLemma f n) }=
% > ( f . (f . flowR f n) ) ={ Refl }=
% > ( f . flowR f (S n) ) QED
%
\noindent
Let's summarize: we have considered the special case of deterministic
......@@ -152,18 +158,15 @@ on a set |X| are functions of type |X -> M X| where |M| is a monad.
%
When |M| is the identity monad, one recovers the deterministic case.
%
%%For |M| equal to |List| one has non-deterministic systems and |M| equal
%%to the finite probability distribution monads |Dist|
%%\citep{10.1017/S0956796805005721} or |SimpleProb|
%%\citep{2017_Botta_Jansson_Ionescu} formalizes the notion of stochastic
%%systems.
When |M| is |List| one has non-deterministic systems, and finite
probability monads (e.g. |Dist| \citep{10.1017/S0956796805005721} or
|SimpleProb| \citep{ionescu2009, 2017_Botta_Jansson_Ionescu}) capture the notion of
stochastic systems.
probability monads
%*TODO: perhaps cite (e.g. |Dist| \citep{10.1017/S0956796805005721} or |SimpleProb| \citep{ionescu2009, 2017_Botta_Jansson_Ionescu})
capture the notion of stochastic systems.
%
\nocite{10.1017/S0956796805005721,ionescu2009, 2017_Botta_Jansson_Ionescu}
%
Other monads encode other notions of uncertainty, see
\citep{ionescu2009,giry1981}.
%Other monads encode other notions of uncertainty, see \citep{ionescu2009,giry1981}.
\nocite{ionescu2009,giry1981}
One can extend the flow (and, as we will see in
section~\ref{section:applications}, other elementary operations) of
......@@ -173,7 +176,7 @@ with |pure| and function composition with Kleisli composition (|>=>|):
> flowMonL : {X : Type} -> {M : Type -> Type} -> Monad M =>
> (X -> M X) -> Nat -> (X -> M X)
> flowMonL f Z = pure
> flowMonL {-"\,"-} f Z = pure
> flowMonL f ( S n) = flowMonL f n >=> f
>
> flowMonR : {X : Type} -> {M : Type -> Type} -> Monad M =>
......@@ -193,11 +196,12 @@ What do we know about Kleisli composition \emph{in general}?
%
We discuss this question in the next two sections but let us
anticipate that, if we require functors to preserve the extensional
equality of arrows (in addition to identity and composition)
and Kleisli composition to fulfil the specification
equality of arrows (in addition to identity and composition) and
Kleisli composition to fulfil the specification
%
\vspace*{-2ex}
\begin{center}
\begin{tikzcd}[row sep=large, column sep=large]
\begin{tikzcd}[column sep=large]
|M C|
& |M (M C)| \arrow[l, "|join|"]
& |M B| \arrow[l, "|map g|"]
......@@ -210,20 +214,6 @@ and Kleisli composition to fulfil the specification
> kleisliSpec : {A, B, C : Type} -> {M : Type -> Type} -> Monad M =>
> (f : A -> M B) -> (g : B -> M C) -> (f >=> g) <=> join . map g . f
% \begin{minipage}{0.4\textwidth}
% \begin{tikzcd}[row sep=large, column sep=large]
% |A| \arrow[r, "|f|"] \arrow[d, "|f>=>g|"] & |M B| \arrow[d, "|map g|"] \\
% |M C| & |M (M C)| \arrow[l, "|join|"]
% \end{tikzcd}
% \end{minipage}
%
% \begin{tikzcd}[row sep=large, column sep=large]
% |A| \arrow[r, "|f|"] \arrow[rrr, bend left=30, "|f>=>g|"]
% & |M B| \arrow[r, "|map g|"]
% & |M (M C)| \arrow[r, "|join|"]
% & |M C|
% \end{tikzcd}
%
then we can derive preservation of extensional equality
> kleisliPresEE : {A, B, C : Type} -> {M : Type -> Type} -> Monad M =>
......@@ -240,7 +230,7 @@ From these premises, we can prove the \emph{extensional} equality of
|flowMonL| and |flowMonR| using a similar lemma as in the deterministic case:
%
> flowMonRLemma : {X : Type} -> {M : Type -> Type} -> Monad M =>
> flowMonRLem : {X : Type} -> {M : Type -> Type} -> Monad M =>
> (f : X -> M X) -> (n : Nat) -> (flowMonR f n >=> f) <=> (f >=> flowMonR f n)
First, notice that the base case of the lemma requires computing
......@@ -262,7 +252,7 @@ Kleisli composition: for |f : A -> M B| we have
%endif
> flowMonRLemma f Z x =
> flowMonRLem f Z x =
> ( (flowMonR f Z >=> f) x ) ={ Refl }=
> ( (pure >=> f) x ) ={ pureLeftIdKleisli f x }=
> ( f x ) ={ sym (pureRightIdKleisli f x) }=
......@@ -273,15 +263,15 @@ As we will see in subsection \ref{def:pureLeftIdKleisli},
|pureLeftIdKleisli| and |pureRightIdKleisli| are either ADT axioms or
theorems, depending of the formulation of the monad ADT.
%
The induction step of |flowMonRLemma| relies on preservation of
The induction step of |flowMonRLem| relies on preservation of
extensional equality and on associativity of Kleisli composition:
> flowMonRLemma f ( S n) x =
> flowMonRLem f ( S n) x =
> let rest = flowMonR f n in
> ( (flowMonR f (S n) >=> f) x ) ={ Refl }=
> ( ((f >=> rest) >=> f) x ) ={ kleisliAssoc f rest f x }=
> ( (f >=> (rest >=> f)) x ) ={ kleisliPresEE f f (rest >=> f) (f >=> rest)
> (\ v => Refl) (flowMonRLemma f n) x }=
> (\ v => Refl) (flowMonRLem f n) x }=
> ( (f >=> (f >=> rest)) x ) ={ Refl }=
> ( (f >=> flowMonR f (S n)) x ) QED
......@@ -298,11 +288,11 @@ Finally, the extensional equality of |flowMonL| and |flowMonR|
> ( flowMonL f (S n) x ) ={ Refl }=
> ( (fLn >=> f) x ) ={ kleisliPresEE fLn fRn f f
> (flowMonLemma f n) (\v => Refl) x }=
> ( (fRn >=> f) x ) ={ flowMonRLemma f n x }=
> ( (fRn >=> f) x ) ={ flowMonRLem f n x }=
> ( (f >=> fRn) x ) ={ Refl }=
> ( flowMonR f (S n) x ) QED
follows from |flowMonRLemma| and, again, preservation of extensional equality.
follows from |flowMonRLem| and, again, preservation of extensional equality.
\paragraph*{Discussion.} Before we turn to the next section, let us discuss one
objection to what we have just done.
......@@ -326,8 +316,9 @@ these would make our monad interface impossible (or at least very
hard) to implement.
%
In general, we cannot rely on |f >=> g| to be intensionally equal to
|join . map g . f| (or, for that matter, to be intensionally equal to
|\a => f a >>= g|).
|join . map g . f|.
% we haven't introduced bind yet...
%(or, for that matter, to be intensionally equal to |\a => f a >>= g|).
In designing ADTs and formulating generic results, we have to be careful
not to impose too strong proof obligations on implementors.
......
2020.Extensional equality preservation and verified generic programming/Functors.lidr
View file @ b4e5227f
......@@ -32,7 +32,7 @@ $\mathcal{D}$ (often both denoted by |F|) such that for each arrow |f
: A -> B| in $\mathcal{C}$ there is an arrow |F f : F A -> F B| in
$\mathcal{D}$.
%
For an introduction to category theory, see \citep{pierce_basic_1991}.
For an introduction to category theory, see \citet{pierce_basic_1991}.
%
The arrow map preserves identity arrows and arrow composition.
%
......@@ -173,7 +173,7 @@ proof looks as follows:
> mapListPresEE : {A, B : Type} -> (f, g : A -> B) -> f <=> g -> mapList f <=> mapList g
> mapListPresEE f g fEEg [] = Refl
> mapListPresEE f g fEEg (a :: as) =
> mapListPresEE f g fEEg (a :: as) = {-"\,"-}
> ( mapList f (a :: as) ) ={ Refl }=
> ( f a :: mapList f as ) ={ cong {f = (::{-"~"-} mapList f as)} (fEEg a) }=
> ( g a :: mapList f as ) ={ cong (mapListPresEE f g fEEg as) }=
......@@ -181,17 +181,15 @@ proof looks as follows:
> ( mapList g (a :: as) ) QED
In general the proofs have a very simple structure: they use the |f
<=> g| arguments to transform the arguments of type |A| expected by
the constructors into arguments of type |B|, and otherwise only use
the induction hypotheses.
<=> g| arguments at the ``leaves'', and otherwise only use the
induction hypotheses.
%
They can also be written as dependent folds, but this results in less
readable proofs.
%They can also be written as dependent folds, but this results in less
%readable proofs.
%
(With a suitable universe of codes for types, or a library for
With a suitable universe of codes for types, or a library for
parametricity proofs, these proofs can be automated using
datatype-generic programming.)
%
datatype-generic programming.
%if False
We can write |mapListPresEE| in a more condensed form using Idris'
......@@ -240,13 +238,13 @@ This is a common pattern for proofs of |mapPresEE|.
%endif
Let's now turn to a type constructor that is not an instance of
|VeriFunctor|, namely |Reader E| for some environment |E : Type|.
our |VeriFunctor|, namely |Reader E| for some environment |E : Type|.
> Reader : Type -> Type -> Type
> Reader E A = E -> A
>
> mapReader : {A, B, E : Type} -> (A -> B) -> Reader E A -> Reader E B
> mapReader f r = f . r
> mapR : {A, B, E : Type} -> (A -> B) -> (Reader E A -> Reader E B)
> mapR f r = f . r
If we try to implement preservation of extensional equality we end up with
......@@ -258,18 +256,17 @@ If we try to implement preservation of extensional equality we end up with
%endif
> mapReaderPresEE : {A, B : Type} -> (f, g : A -> B) ->
> f <=> g -> mapReader f <=> mapReader g
> mapReaderPresEE f g fEEg r =
> ( mapReader f r) ={ Refl }=
> mapRPresEE : {A, B : Type} -> (f, g : A -> B) -> f <=> g -> mapR f <=> mapR g
> mapRPresEE f g fEEg r =
> ( mapR f r) ={ Refl }=
> ( f . r ) ={ whatnow1 r }= -- here we need |f = g| to proceed
> ( g . r ) ={ Refl }=
> ( mapReader g r) QED
> ( mapR g r) QED
Notice the question mark in front of |whatnow1r|. This introduces an
unresolved proof step and allows us to ask Idris to help us implementing
this step, see ``Elaborator Reflection -- Holes'' in \citep{idrisdocs}.
Among others, we can ask about the
Among other things, we can ask about the
type of |whatnow1r|. Perhaps not surprisingly, this turns out to be |f
. r = g . r|.
......@@ -278,9 +275,6 @@ all |e : E|, we cannot deduce |f . r = g . r| without extensionality.
%
Thus |Reader E| does not implement the |VeriFunctor| interface, but it
is ``very close''.
%
\footnote{By a similar argument, |mapPresEE| does not hold for the
continuation monad.}
%if False
> (<==>) : {A, B, C : Type} -> (f, g : A -> B -> C) -> Type
......@@ -290,13 +284,16 @@ is ``very close''.
Using the 2-argument version of function extensionality |(<==>) =
extify (<=>)| it is easy to show
> mapReaderPresEE2 : {E, A, B : Type} -> (f, g : A -> B) ->
> f <=> g -> mapReader f <==> mapReader g
> mapReaderPresEE2 f g fEEg r x = fEEg (r x)
> mapRPresEE2 : {E, A, B : Type} -> (f, g : A -> B) -> f <=> g -> mapR f <==> mapR g
> mapRPresEE2 f g fEEg r x = fEEg (r x)
Thus, |Reader E| is an example of a functor which does not preserve,
but rather \emph{transforms} the notion of equality.
%
By a similar argument, |mapPresEE| does not hold for the continuation
monad.
%
As we mentioned earlier, it is tempting to start adding equalities to
the interface (towards a setoid-based framework), but this is not a
path we take here.
......
2020.Extensional equality preservation and verified generic programming/Monads.lidr
View file @ b4e5227f
......@@ -32,7 +32,7 @@ We discuss the role of extensional equality preservation for deriving
monad laws and for verifying the equivalence between the different ADT
formulations.
%
There are many possible way of formulating Monad axioms. Here, we do not
There are many possible ways of formulating Monad axioms. Here, we do not
argue for or against a specific formulation but rather discuss the most
popular ones and their trade-offs.
......@@ -220,6 +220,8 @@ underlying functor, as one would expect.
%endif
\begin{joincode}%
> kleisliPresEE : {A, B, C : Type} -> {M : Type -> Type} -> ThinVeriMonad M =>
> (f, f' : A -> M B) -> (g, g' : B -> M C) ->
> f <=> f' -> g <=> g' -> (f >=> g) <=> (f' >=> g')
......@@ -245,6 +247,8 @@ underlying functor, as one would expect.
> ( (join . map g') (f' a) ) ={ Refl }=
> ( (f' >=> g') a ) QED
\end{joincode}
In the implementation of |kleisliPresEE|, we have
applied the ``leapfrogging'' rule (compare \citep{bird2014thinking},
p. 250):
......@@ -335,7 +339,7 @@ better.
This suggests that an alternative way of formalizing the traditional
notion of monads from category theory could be through a \emph{fat} ADT:
%\newpage
\pagebreak
%if False
> namespace Fat
......@@ -377,8 +381,7 @@ Thus, for instance |pureLeftIdKleisli| becomes
> pureLeftIdKleisli : {A, B : Type} -> {M : Type -> Type} -> Fat.VeriMonadFat M =>
> (f : A -> M B) -> (pure >=> f) <=> f
> pureLeftIdKleisli f a =
> ( (pure >=> f) a ) ={ kleisliJoinMapSpec pure f a }=
> pureLeftIdKleisli f a = ( (pure >=> f) a ) ={ kleisliJoinMapSpec pure f a }=
> ( join (map f (pure a)) ) ={ cong {f = join} (Fat.pureNatTrans f a) }=
> ( join (pure (f a)) ) ={ Fat.triangleLeft (f a) }=
> ( f a ) QED
......@@ -543,7 +546,7 @@ The lifting operation is required to satisfy W1--W3 for any objects
\paragraph*{From tradition to Wadler and back.}
%
The two monad definitions can be seen as views on the same mathematical
The two monad definitions can be seen as two views on the same mathematical
concept and we would like the corresponding ADT formulations to preserve
this relationship.
......@@ -657,7 +660,7 @@ composition.
The moral is that, even if we adopt the Wadler view on monads and a more
economical specification, we have to require |lift| to preserve
extensional equality if our specification has to be consistent with the
extensional equality if we want our specification to be consistent with the
traditional one.
This completes the discussion on different notions of monads and on the
......@@ -679,9 +682,9 @@ We discuss more examples of applications of the principle in the
context of DSLs for dynamical systems theory in section \ref{section:applications}.
%
In the rest of this section, we prepare by deriving two intermediate
results. % in the context of the traditional view on monads.
properties. % in the context of the traditional view on monads.
%
The first result is the extensional equality between |map f . join
The first is the extensional equality between |map f . join
. map g| and |join . map (map f . g)|:
< mapJoinLemma : {M : Type -> Type} -> {A, B, C : Type} -> Fat.VeriMonadFat M =>
......@@ -693,7 +696,7 @@ The first result is the extensional equality between |map f . join
< ( join ((map (map f) . (map g)) ma) ) ={ cong (sym (mapPresComp (map f) g ma)) }=
< ( join (map (map f . g) ma) ) QED
The second result
The second,
< mapKleisliLemma : {A, B, C, D : Type} -> {M : Type -> Type} -> Fat.VeriMonadFat M =>
< (f : A -> M B) -> (g : B -> M C) -> (h : C -> D) ->
......@@ -704,7 +707,7 @@ The second result
< ( join (map (map h . g) (f ma)) ) ={ sym (kleisliJoinMapSpec f (map h . g) ma) }=
< ( (f >=> map h . g) ma ) QED
can be seen to be an associativity law by rewriting it in terms of
can be seen as an associativity law by rewriting it in terms of
|(<=<) = flip (>=>)|:
%if False
......
2020.Extensional equality preservation and verified generic programming/RelatedWork.lidr
View file @ b4e5227f
......@@ -33,7 +33,7 @@ The price to pay when using a full-fledged setoid approach is the
presence of a potentially huge amount of additional proof obligations,
needed to coherently deal with sets (types) and their equivalence
relations -- this often is pointedly referred to as \emph{setoid hell}
(for instance in \citep{altenkirch_setoidhell}, but it seems to have
(for instance in \citet{altenkirch_setoidhell}, but it seems to have
been used colloquially in the community for much longer).
Still, there are some large developments using setoids, e.g. the CoRN
......@@ -99,11 +99,11 @@ preservation but not preservation of extensional equality
(minimal) interfaces that we only exemplified using verified monads.
%
Regarding the relation between different representations of monads, the reader
might contrast the approach in
\citep[\texttt{CategoryTheory.Monads.KTriplesEquiv}]{UniMath} with our approach
might contrast the approach in the UniMath
\citep[\texttt{CategoryTheory.Monads.KTriplesEquiv}]{UniMath} library with our approach
in section~\ref{section:monads}. The UniMath development is part of a
full-fledged formalization of category theory and relates "the traditional view"
with the "Wadler view" of a monad (as we called them) via a weak equivalence of
full-fledged formalization of category theory and relates ``the traditional view''
with the ``Wadler view'' of a monad (as we called them) via a weak equivalence of
categories. This approach is very satisfactory from an abstract mathematical
perspective.
%
......
2020.Extensional equality preservation and verified generic programming/main.lhs
View file @ b4e5227f
......@@ -117,8 +117,9 @@ generic programming.
%include Conclusions.lidr
\section*{Acknowledgments}
%**PJ[after review]: The authors thank the JFP editors and reviewers, whose comments have
%lead to significant improvements of the original manuscript.
The authors thank the JFP editors and reviewers, whose comments have
lead to significant improvements of the original manuscript.
%
The work presented in this paper heavily relies on free software, among others on Coq, Idris, Agda, GHC, git, vi, Emacs, \LaTeX\ and on the FreeBSD and Debian GNU/Linux operating systems.
%
......
2020.Extensional equality preservation and verified generic programming/references.bib
View file @ b4e5227f
......@@ -898,7 +898,8 @@ isbn="978-3-540-27818-4"
univalent mathematics},
url = {https://github.com/UniMath/UniMath},
howpublished = {Available at
\url{https://github.com/UniMath/UniMath}}
\url{https://github.com/UniMath/UniMath}},
year = {2021}
}
@book{pierce_basic_1991,
......
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