Update exercise instructions (#93)

Author: eloots

exercises/exercise_010_opaque_type_aliases/README.md

@@ -8,8 +8,8 @@ any runtime overhead. The aim is to provide additional type-safety at
 compile-time but then be stripped away at runtime. It is a powerful new feature
 of Scala 3 for supporting Information Hiding.
 
-Opaque Type Aliases differ from plain Scala 2 Type Aliases in that the later
-just provide a new name for a type but wherever this new name is used, the
+Opaque Type Aliases differ from plain Scala 2 Type Aliases in that the latter
+just provides a new name for a type but wherever this new name is used, the
 call-site still knows the details of the original type being aliased. With
 Opaque Type Aliases, the original type being aliased is hidden (or is opaque) at
 the call-site.
@@ -31,14 +31,13 @@ type CellUpdates = Vector[(Int, Set[Int])]
 ```
 
 To keep things manageable we will only focus on one of these type aliases for
-this exercise. Specifically we will convert the last of these type aliases,
-`ReductionSet` into an Opaque Type Alias.
+this exercise. Specifically we will convert the `ReductionSet` type aliases
+into an Opaque Type Alias.
 
-- Start by moving the type alias to a new source file, `ReductionSet`.
+- Start by moving the type alias to a new source file, `ReductionSet.scala`.
 
-- Now add the keyword `opaque` in front of the type alias
-  declaration and recompile. Do you expect this to compile successfully? If not,
-  why?
+- Now add the keyword `opaque` in front of the type alias declaration and
+  recompile. Do you expect this to compile successfully? If not, why?
 
 - So it seems we need to tackle quite a few compilation errors... Let's get
   started.
@@ -47,30 +46,30 @@ this exercise. Specifically we will convert the last of these type aliases,
 >      `value {name} is not a member of ...` before tackling the other types
 >      of error like `Found: ... Required: ...`
 
-- The first errors are in the source file `ReductionRules`. As this file contains
-  two extension methods on `ReductionSet`, moving these to `ReductionSet` will
-  resolve these errors.
+- The first errors are in the source file `ReductionRules.scala`. As this file
+  contains two extension methods on `ReductionSet`, moving these to `ReductionSet`
+  will resolve these errors.
 
-- Next up is an error linked to value `InitialDetailState`. It's an
-  `InitialDetailState` which is a `ReductionSet`. Again, move it to the
-   `ReductionSet` source file. You may have to annotate its type.
+- Next up is an error linked to value `InitialDetailState`. It's a `ReductionSet`,
+  so again, move it to the `ReductionSet.scala` source file. You may have to
+  annotate its type.
 
-- Recompile and look at the first few error in source file `SudokuDetailProcessor`.
+- Recompile and look at the first few error in source file `SudokuDetailProcessor.scala`.
   These are linked to methods `mergeState`, `stateChanges`, and `isFullyReduced`.
   As these 3 methods all take a `ReductionSet` as argument, it makes sense to
   convert them to extension methods on `ReductionSet`. Do so, and adapt the
-  call sites to take the change into account. Note that you may have to change
+  call sites to take this change into account. Note that you may have to change
   the visibility of the methods.
 
-- Recompile and notice the errors in `SudokuIO`. The relevant code is doing some
+- Recompile and notice the errors in `SudokuIO.scala`. The relevant code is doing some
   kind of pretty print of a `Vector[ReductionSet]` (which is a `Sudoku`; see the
   type alias in `TopLevelDefinitions`). Move the method `SudokuRowPrinter` to
   `ReductionSet` and convert it to an extension method (name it `printSudokuRow`).
   Move the private `sudokuCellRepresentation` helper method along with it. Make
   the necessary changes at the call site.
 
 - Recompile. Notice the extension methods on `SudokuField` that are now in error.
-  Move these to `ReductionSet` and recompile. Methods `randomSwapAround` and
+  Move these to `ReductionSet.scala` and recompile. Methods `randomSwapAround` and
   `toRowUpdates` show errors.
 
 - The core issue with method `randomSwapAround` is the mapping on a `ReductionSet`.
@@ -79,9 +78,10 @@ this exercise. Specifically we will convert the last of these type aliases,
   Make the necessary changes to `randomSwapAround` to make it compile.
 
 - The core issue with method `toRowUpdates` is invoking `zipWithIndex` on `ReductionSet`.
-  Add a private extension method `zipWithIndex` on `ReductionSet`.
+  Add a _private_ extension method `zipWithIndex` on `ReductionSet`. What should its
+  return type be?
 
-- We've almost eliminated all complilation errors. The last error can be corrected
+- We've almost eliminated all compilation errors. The last error can be corrected
   by adding an apply method in a `ReductionSet` companion object that allows
   one to create a `ReductionSet` from a `Vector[CellContent]`.
 
@@ -99,13 +99,9 @@ It does raise some questions:
 - Was it worth the effort?
   - What have we gained, if anything?
 - Are there alternatives to this approach?
-- What are the gotchas 
-
-There are many more potential type aliases to which we could apply the same
-procedure. One that sticks out is the `Sudoku` type alias
-(`type Sudoku = Vector[ReductionSet`).
-
-
-
+- What are the gotchas
 
+There are more type aliases in the source code that potentially could be converted to
+opaque versions. One that sticks out is the `Sudoku` type alias
+(`type Sudoku = Vector[ReductionSet`). You may want to take a stab at converting it...
 

exercises/exercise_011_multiversal_equality/README.md

@@ -28,12 +28,13 @@ error.
 ## Steps
 
 - Enable multiversal equality at the project level by adding `-language:strictEquality`
-  to the Scalaa compiler options in `project/Build.scala`
+  to the Scala compiler options in `project/Build.scala`
 
 - Use the course notes on Multiversal Equality and your experience from the
   exercise on `given`s to make the code compile with the flag
   `-language:strictEquality` enabled
     - Hint: The simplest solution will probably involve using `CanEqual.derived`
 
 - Run the provided tests by executing the `test` command from the `sbt` prompt
-  and verify that all tests pass
+  and verify that all tests pass
+