Merge branch 'develop-deprecate-arrayAccess'. Close #599.

**Description**

The functions `copilot-language:Copilot.Language.Operators.Array.(.!!)` and
`copilot-libraries:Copilot.Library.Utils.(!!)` were deprecated due to the
introduction of a new, common interface to interact with structures and arrays.

The original functions were deprecated in Copilot 4 and no messages have been
received requesting that they be kept in this library.

As per our internal policy of waiting 3 versions from deprecation until a
public interface declaration can be removed, these functions can now be
removed.

**Type**

- Management: remove code deprecated by the introduction of a new feature.

**Additional context**

- Issue #36, addressed in Copilot 4, deprecated the functions.

**Requester**

- Ivan Perez

**Method to check presence of bug**

Not applicable (not a bug).

**Expected result**

Running either of the checks above prints a message indicating that the
functions imported do not exist.

Running either of the checks above prints a message indicating that the
functions imported do not exist. Either of the following should trigger errors:

```
$ runhaskell <<< 'import Copilot.Language.Operators.Array((.!!)); main = return ()'
$ runhaskell <<< 'import Copilot.Library.Utils ((!!)); main = return ()'
```

The following Dockerfile tries to import the deprecated functions, succeeding
only when the import fails, after which prints the message "Success":

```
FROM ubuntu:focal

ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update

RUN apt-get install --yes \
      libz-dev \
      git \
      curl \
      gcc \
      g++ \
      make \
      libgmp3-dev  \
      pkg-config \
      z3

RUN mkdir -p $HOME/.ghcup/bin
RUN curl https://downloads.haskell.org/~ghcup/0.1.40.0/x86_64-linux-ghcup-0.1.40.0 -o $HOME/.ghcup/bin/ghcup
RUN chmod a+x $HOME/.ghcup/bin/ghcup
ENV PATH=$PATH:/root/.ghcup/bin/
ENV PATH=$PATH:/root/.cabal/bin/

SHELL ["/bin/bash", "-c"]

RUN ghcup install ghc 9.10.1
RUN ghcup install cabal 3.2
RUN ghcup set ghc 9.10.1
RUN cabal update

SHELL ["/bin/bash", "-c"]
CMD git clone $REPO && cd $NAME && git checkout $COMMIT && cd .. \
  && cabal v1-sandbox init \
  && cabal v1-install alex happy --constraint='happy <= 2' \
  && cabal v1-install $NAME/copilot**/ \
  && ! cabal v1-exec -- runhaskell <<< 'import Copilot.Language.Operators.Array((.!!)); main = return ()' \
  && ! cabal v1-exec -- runhaskell <<< 'import Copilot.Library.Utils ((!!)); main = return ()' \
  && echo "Success"
```

Command (substitute variables based on new path after merge):
```
$ docker run -e "REPO=https://github.com/Copilot-Language/copilot" -e "NAME=copilot" -e "COMMIT=<HASH>" -it copilot-verify-599
```

**Solution implemented**

Remove the deprecated functions
`copilot-language:Copilot.Language.Operators.Array.(.!!)` and
`copilot-libraries:Copilot.Library.Utils.(!!)` , and any references to them.

**Further notes**

None.

Author: ivanperez-keera

copilot-language/CHANGELOG

@@ -1,6 +1,8 @@
-2025-02-28
+2025-03-07
         * Fix typo in documentation. (#587)
         * Record how a Property's underlying proposition is quantified. (#254)
+        * Remove deprecated function Copilot.Language.Operators.Array.(.!!).
+          (#599)
 
 2025-01-07
         * Version bump (4.2). (#577)

copilot-language/src/Copilot/Language/Operators/Array.hs

@@ -8,8 +8,7 @@
 
 -- | Combinators to deal with streams carrying arrays.
 module Copilot.Language.Operators.Array
-  ( (.!!)
-  , (!)
+  ( (!)
   , (!!)
   , (=:)
   , (=$)
@@ -34,18 +33,6 @@ import Prelude      hiding ((!!))
     => Stream (Array n t) -> Stream Word32 -> Stream t
 arr ! n = Op2 (Index typeOf) arr n
 
--- | Create a stream that carries an element of an array in another stream.
---
--- This function implements a projection of the element of an array at a given
--- position, over time. For example, if @s@ is a stream of type @Stream (Array
--- '5 Word8)@, then @s .!! 3@ has type @Stream Word8@ and contains the 3rd
--- element (starting from zero) of the arrays in @s@ at any point in time.
-{-# DEPRECATED (.!!) "This function is deprecated in Copilot 4. Use (!)." #-}
-(.!!) :: ( KnownNat n
-         , Typed t
-         ) => Stream (Array n t) -> Stream Word32 -> Stream t
-(.!!) = (!)
-
 -- | Pair a stream with an element accessor, without applying it to obtain the
 -- value of the element.
 --

copilot-libraries/CHANGELOG

@@ -1,3 +1,6 @@
+2025-03-07
+        * Remove deprecated function Copilot.Library.Utils.(!!). (#599)
+
 2025-01-07
         * Version bump (4.2). (#577)
         * Bump upper version constraint on containers. (#570)

copilot-libraries/src/Copilot/Library/Libraries.hs

@@ -23,6 +23,6 @@ import Copilot.Library.LTL
 import Copilot.Library.PTLTL
 import Copilot.Library.Statistics
 import Copilot.Library.RegExp
-import Copilot.Library.Utils      hiding ((!!))
+import Copilot.Library.Utils
 import Copilot.Library.Voting
 import Copilot.Library.Stacks

copilot-libraries/src/Copilot/Library/Utils.hs

@@ -13,10 +13,10 @@ module Copilot.Library.Utils
          -- ** Scans
          nscanl, nscanr, nscanl1, nscanr1,
          -- ** Indexing
-         case', (!!), (!!!))
+         case', (!!!))
 where
 
-import Copilot.Language hiding ((!!))
+import Copilot.Language
 import qualified Prelude as P
 
 -- | Given a stream, produce an infinite list of streams dropping an increasing
@@ -131,13 +131,6 @@ case' predicates alternatives =
                    P.++ "greater by one than the length of predicates list"
   in case'' predicates alternatives
 
--- | Index.
---
--- WARNING: Very expensive! Consider using this only for very short lists.
-(!!) :: (Typed a, Eq b, Num b, Typed b) => [Stream a] -> Stream b -> Stream a
-(!!) = (!!!)
-{-# DEPRECATED (!!) "This function is deprecated in Copilot 4. Use (!!!)." #-}
-
 -- | Index.
 --
 -- WARNING: Very expensive! Consider using this only for very short lists.