presentation: more progress

presentation/main.tex

@@ -206,17 +206,18 @@ end
       Traits are subordinate to \emph{object-oriented} classes.
     }
     \note[item]{
-      The authors of the seminal paper on traits present them as subordinate to object-oriented
-      classes; traits can't imply each other, which we'll discuss more later on.
+      Sch{\"a}rli et al. present as subordinate to object oriented classes
+    }
+    \note[item]{
+      Different problem domain; can't have traits imply other traits
     }
 
     \item<3->{
       The "type ownership" problem is baked in to the existing theory.
     }
     \note[item]{
-      Given the motivation of traits as subordinate to object-oriened classes, it makes sense that
-      you must own a type to implement a trait, since you'll almost always own all of a class
-      hierarchy.
+      Since traits were developed alongside object-oriented classes, there was no need to allow
+      instances for types not owned by the programmer
     }
   \end{itemize}
 
@@ -499,8 +500,8 @@ instance Collectible $\alpha$ list where
   \begin{onlyenv}<4->
     \vspace{-16pt}
     \begin{lstlisting}[mathescape=true]
-for x in [1, 2, 3, 4]: int list
-  collect (fn x => x + 1)
+for x in [1, 2, 3, 4] $\arrow$ int list
+  collect (x + 1)
     \end{lstlisting}
   \end{onlyenv}
   \note[item]{
@@ -518,7 +519,7 @@ instance Collectible string where
   val default = ""
   val insert = concat
 
-for x in ["hi", " ", "world", "!"]: string
+for x in ["hi", " ", "world", "!"] $\arrow$ string
   collect x
   \end{lstlisting}
   \note[item]{
@@ -534,7 +535,7 @@ for x in ["hi", " ", "world", "!"]: string
 \begin{frame}[fragile]{Desired design}
   How about \tt{filter}?
   \begin{lstlisting}[mathescape=true]
-for id in users: string list
+for id in users $\arrow$ string list
   if registered? id
   then collect id
   else pass
@@ -1038,7 +1039,7 @@ instance Iterable string where
   Recall our desired designs:
   \begin{lstlisting}[mathescape=true]
 for x in [1, 2, 3, 4] $\arrow$ int list
-  collect (fn x => x + 1)
+  collect (x + 1)
 
 for x in ["hi", " ", "world", "!"] $\arrow$ string
   collect x
@@ -1062,7 +1063,7 @@ for id in users $\arrow$ string list
 
 \begin{frame}[fragile]{Iteration: \texttt{\Large for} formalism}
   \begin{lstlisting}[mathescape=true]
-for <var> in <collection>: <ty>
+for <var> in <collection> $\arrow$ <ty>
     <expr>
   \end{lstlisting}
 
@@ -1159,6 +1160,27 @@ pass
 \end{frame}
 
 
+\begin{frame}[fragile]{Iteration: big payoff!}
+  \begin{lstlisting}[mathescape=true]
+val pass = fn _ => None
+val collect = fn x => Some x
+val for = fn var collection $\iota$ expr =>
+  case (next collection)
+    of None => $\iota$
+     | Some (item, rest) =>
+         case (expr item)
+           of Some item' => for var rest (insert $\iota$ item') expr
+            | None => for var rest $\iota$ expr
+  \end{lstlisting}
+
+  \begin{onlyenv}<2->
+    \begin{lstlisting}[mathescape=true]
+<expr> $\mapsto$ fn <var> => <expr>
+    \end{lstlisting}
+  \end{onlyenv}
+\end{frame}
+
+
 \begin{frame}{}
   \begin{center}
     \Large Thank you!