# HG changeset patch
# User Christian Urban <christian dot urban at kcl dot ac dot uk>
# Date 1476706714 -3600
# Node ID b93f4d2aeee1bcde50dfb329ace128c995e13fac
# Parent  4a5876f321aeece97ff23fde5b66a346f4892710
updated

diff -r 4a5876f321ae -r b93f4d2aeee1 handouts/ho01.tex
--- a/handouts/ho01.tex	Sat Oct 15 14:27:01 2016 +0100
+++ b/handouts/ho01.tex	Mon Oct 17 13:18:34 2016 +0100
@@ -27,23 +27,6 @@
 %%  reasons for a new prgramming language
 %% http://beautifulracket.com
 
-%regher
-% We can start off with a couple of observations about the role of
-% compilers. First, hardware is getting weirder rather than getting
-% clocked faster: almost all processors are multicores and it looks
-% like there is increasing asymmetry in resources across
-% cores. Processors come with vector units, crypto accelerators, bit
-% twiddling instructions, and lots of features to make virtualization
-% and concurrency work. We have DSPs, GPUs, big.little, and Xeon
-% Phi. This is only scratching the surface. Second, we’re getting
-% tired of low-level languages and their associated security
-% disasters, we want to write new code, to whatever extent possible,
-% in safer, higher-level languages. Compilers are caught right in the
-% middle of these opposing trends: one of their main jobs is to help
-% bridge the large and growing gap between increasingly high-level
-% languages and increasingly wacky platforms. It’s effectively a
-% perpetual employment act for solid compiler hackers.
-
 % compiler explorer
 % https://gcc.godbolt.org
 
diff -r 4a5876f321ae -r b93f4d2aeee1 handouts/ho07.pdf
Binary file handouts/ho07.pdf has changed
diff -r 4a5876f321ae -r b93f4d2aeee1 handouts/ho07.tex
--- a/handouts/ho07.tex	Sat Oct 15 14:27:01 2016 +0100
+++ b/handouts/ho07.tex	Mon Oct 17 13:18:34 2016 +0100
@@ -17,15 +17,33 @@
 the fastest possible code, but code that is fast enough and
 has the advantage that the virtual machine takes care of
 things a compiler would normally need to take care of (like
-explicit memory management).
+explicit memory management). Why study compilers? John Regher
+gives this answer in his compiler blog:\footnote{\url{http://blog.regehr.org/archives/1419}}
 
-As a first example we will implement a compiler for the very
-simple While-language. It will generate code for the Java
-Virtual Machine (JVM). This is a stack-based virtual machine,
-a fact which will make it easy to generate code for arithmetic
-expressions. For example for generating code for the
-expression $1 + 2$ we need to generate the following three
-instructions
+\begin{quote}\it{}``We can start off with a couple of observations
+  about the role of compilers. First, hardware is getting weirder
+  rather than getting clocked faster: almost all processors are
+  multicores and it looks like there is increasing asymmetry in
+  resources across cores. Processors come with vector units, crypto
+  accelerators, bit twiddling instructions, and lots of features to
+  make virtualization and concurrency work. We have DSPs, GPUs,
+  big.little, and Xeon Phi. This is only scratching the
+  surface. Second, we’re getting tired of low-level languages and
+  their associated security disasters, we want to write new code, to
+  whatever extent possible, in safer, higher-level
+  languages. Compilers are caught right in the middle of these
+  opposing trends: one of their main jobs is to help bridge the large
+  and growing gap between increasingly high-level languages and
+  increasingly wacky platforms. It’s effectively a perpetual
+  employment act for solid compiler hackers.''
+\end{quote}  
+
+As a first example in this module we will implement a compiler for the
+very simple While-language. It will generate code for the Java Virtual
+Machine (JVM). This is a stack-based virtual machine, a fact which
+will make it easy to generate code for arithmetic expressions. For
+example for generating code for the expression $1 + 2$ we need to
+generate the following three instructions
 
 \begin{lstlisting}[numbers=none]
 ldc 1
diff -r 4a5876f321ae -r b93f4d2aeee1 slides/slides04.pdf
Binary file slides/slides04.pdf has changed
diff -r 4a5876f321ae -r b93f4d2aeee1 slides/slides04.tex
--- a/slides/slides04.tex	Sat Oct 15 14:27:01 2016 +0100
+++ b/slides/slides04.tex	Mon Oct 17 13:18:34 2016 +0100
@@ -936,13 +936,13 @@
   \bl{$(\ZERO \cdot (b \cdot c)) + ((\ZERO \cdot c) + \ONE)$}
   \end{center}
 
-  and answer
+  and answer how this regular expression matches the empty string
 
   \begin{center}
   \bl{$Right(Right(Empty))$}
   \end{center}\bigskip
 
-  But now we simplify to \bl{$\ONE$} and produce \bl{$Empty$}.
+  But now we simplify this to \bl{$\ONE$} and would produce \bl{$Empty$}.
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%