Polish

Advanced/Compression/main.tex

@@ -2,8 +2,7 @@
 % use [solutions] flag to show solutions.
 \documentclass[
 	solutions,
-	singlenumbering,
-	unfinished
+	singlenumbering
 ]{../../resources/ormc_handout}
 \usepackage{../../resources/macros}
 

Advanced/Compression/parts/0 intro.tex

@@ -27,8 +27,9 @@ How many bits will we need? \par
 
 
 \problem{}<naivelen>
-Similarly, we can use a na\"ive coding scheme to encode an $n$-symbol string over an alphabet of size $k$ \par
-using $n \times \lceil \log_2k \rceil$ bits. Convince yourself that this is true.
+Similarly, we can encode an $n$-symbol string over an alphabet of size $k$ \par
+using $n \times \lceil \log_2k \rceil$ bits. Show that this is true. \par
+\note[Note]{We'll call this the \textit{na\"ive coding scheme}.}
 
 
 \vfill

Advanced/Compression/parts/1 runlength.tex

@@ -49,8 +49,13 @@ Using a na\"ive coding scheme, encode \texttt{AAAA$\cdot$AAAA$\cdot$BCD$\cdot$AA
 
 \vfill
 In \ref{runlenone}---and often, in the real world---the strings we want to encode have fairly low \textit{entropy}. \par
-They have predictable patterns, sequences of symbols that don't contain a lot of information. \par
-We can exploit this fact to develop efficient encoding schemes.
+That is, they have predictable patterns, sequences of symbols that don't contain a lot of information. \par
+\note{
+	For example, consider the text in this document. \par
+	The symbols \texttt{e}, \texttt{t}, and \texttt{<space>} are much more common than any others. \par
+	Also, certain subsequences are repeated: \texttt{th}, \texttt{and}, \texttt{encode}, and so on.
+}
+We can exploit this fact to develop encoding schemes that need relatively few bits per letter.
 
 \example{}
 A simple example of such a coding scheme is \textit{run-length encoding}. Instead of simply listing letters of a string
@@ -88,10 +93,18 @@ We'll encode our string into a sequence of 6-bit blocks, interpreted as follows:
 \end{center}
 So, the sequence \texttt{BBB} will be encoded as \texttt{[0011-01]}. \par
 \note[Notation]{
-	Just like dots, dashes and spaces are added for readability. \par
+	Just like dots, dashes and spaces are added for readability. Pretend they don't exist. \par
 	Encoded binary sequences will always be written in square brackets. \texttt{[]}.
 }
 
+\problem{}
+Decode \texttt{[010000001111]} using this scheme.
+
+\begin{solution}
+	\texttt{AAAADDD}
+\end{solution}
+\vfill
+
 \problem{}
 Encode \texttt{AAAA$\cdot$AAAA$\cdot$BCD$\cdot$AAAA$\cdot$AAAA} using this scheme. \par
 Is this more or less efficient than \ref{runlenone}?
@@ -109,12 +122,26 @@ Is this more or less efficient than \ref{runlenone}?
 
 
 
+\problem{}
+Give an example of a message on $\{\texttt{A}, \texttt{B}, \texttt{C}, \texttt{D}\}$
+that uses $n$ bits when encoded with a na\"ive scheme, and \textit{fewer} than $\nicefrac{n}{2}$ bits
+when encoded using the scheme described on the previous page.
 
 
+\vfill
+
+\problem{}
+Give an example of a message on $\{\texttt{A}, \texttt{B}, \texttt{C}, \texttt{D}\}$
+that uses $n$ bits when encoded with a na\"ive scheme, and \textit{more} than $2n$ bits
+when encoded using the scheme described on the previous page.
+
+
+\vfill
 
 
 \problem{}
-Is run-length coding always efficient? When does it work well, and when does it fail?
+Is run-length coding always more efficient than na\"ive coding? \par
+When does it work well, and when does it fail?
 
 \vfill
 

Advanced/Compression/parts/2 lzss.tex

@@ -21,7 +21,8 @@ Pointers take the form \texttt{<pos, len>}, where \texttt{pos} is the position o
 For example, we can encode the string \texttt{ABRACADABRA} as \texttt{[ABRACAD<7, 4>]}. \par
 The pointer \texttt{<7, 4>} tells us to look back 7 positions (to the first \texttt{A}), and copy the next 4 symbols. \par
 Note that pointers refer to the partially decoded output---\textit{not} to the encoded string. \par
-This allows pointers to reference other pointers, and ensures that codes like \texttt{A<1,9>} are valid.
+This allows pointers to reference other pointers, and ensures that codes like \texttt{A<1,9>} are valid. \par
+\note{For example, \texttt{[B<1,2>]} decodes to \texttt{BBB}.}
 
 \problem{}
 Encode \texttt{ABCD$\cdot$ABCD$\cdot$BABABA$\cdot$ABCD$\cdot$ABCD} using this scheme. \par