Can now divide using /<space> (#98)

closes #63 and #87

pills/04-basics-of-language.xml

@@ -60,8 +60,7 @@
 
     <para>
       Launch <literal>nix repl</literal>. First of all, Nix supports basic arithmetic operations:
-      <literal>+</literal>, <literal>-</literal>, and <literal>*</literal>. Integer division can be
-      done with <literal>builtins.div</literal>.
+      <literal>+</literal>, <literal>-</literal>, <literal>*</literal> and <literal>/</literal>.
       (To exit <literal>nix repl</literal>, use the command <literal>:q</literal>.
       Help is available through the <literal>:?</literal> command.)
     </para>
@@ -69,16 +68,23 @@
     <screen><xi:include href="./04/basics.txt" parse="text" /></screen>
 
     <para>
-      You might wonder why Nix doesn't have basic operations such as integer division. The answer is
-      because it's not needed for creating packages. Nix is not a general purpose
-      language, it's a domain-specific language for writing packages.
+      Attempting to perform division in Nix can lead to some surprises.
     </para>
 
+    <screen><xi:include href="./04/relative-path.txt" parse="text" /></screen>
+
     <para>
-      Just think - <literal>builtins.div</literal> is not used in the whole of the
-      nixpkgs repository: it's not actually useful if you are writing package expressions.
+      What happened? Recall that Nix is not a general purpose language, it's a
+      domain-specific language for writing packages. Integer division isn't
+      actually that useful when writing package expressions. Nix parsed
+      <literal>6/3</literal> as a relative path to the current directory. To get
+      Nix to perform division instead, leave a space after the
+      <literal>/</literal>. Alternatively, you can use
+      <literal>builtins.div</literal>.
     </para>
 
+    <screen><xi:include href="./04/division.txt" parse="text" /></screen>
+
     <para>
       Other operators are <literal>||</literal>, <literal>&amp;&amp;</literal> and <literal>!</literal>
       for booleans, and relational
@@ -101,15 +107,10 @@
     </para>
 
     <para>
-      Try to use <literal>/</literal> between two numbers:
-    </para>
-
-    <screen><xi:include href="./04/relative-path.txt" parse="text" /></screen>
-
-    <para>
-      Nix parsed <literal>2/3</literal> as a relative path to the current directory. Expressions will
-      be parsed as paths as long as there's a slash. Therefore to specify the current
-      directory, use <literal>./.</literal> In addition, Nix also parses urls specially.
+      As demonstrated above, expressions will
+      be parsed as paths as long as there's a slash not followed by a space.
+      Therefore to specify the current directory, use <literal>./.</literal>
+      In addition, Nix also parses urls specially.
     </para>
 
     <para>

pills/04/basics.txt

@@ -1,4 +1,8 @@
 nix-repl> 1+3
 4
-nix-repl> builtins.div 6 3
-2
+
+nix-repl> 7-4
+3
+
+nix-repl> 3*2
+6

pills/04/division.txt

@@ -0,0 +1,5 @@
+nix-repl> 6/ 3
+2
+
+nix-repl> builtins.div 6 3
+2

pills/04/relative-path.txt

@@ -1,2 +1,2 @@
-nix-repl> 2/3
-/home/nix/2/3
+nix-repl> 6/3
+/home/nix/6/3

pills/08-generic-builders.xml

@@ -231,6 +231,7 @@
     <screen><xi:include href="./08/set-union.txt" parse="text" /></screen>
 
     <para>
+      <emphasis role="bold">Exercise:</emphasis>
       Complete the new <filename>builder.sh</filename> by adding
       <code>$baseInputs</code> in the <code>for</code> loop together with
       <code>$buildInputs</code>. As you noticed, we passed that new variable in

pills/09-automatic-runtime.xml

@@ -208,7 +208,8 @@
     <para>
       That is, for each file we run <command>patchelf --shrink-rpath</command>
       and <command>strip</command>. Note that we used two new commands here,
-      <command>find</command> and <command>patchelf</command>. These two
+      <command>find</command> and <command>patchelf</command>.
+      <emphasis role="bold">Exercise:</emphasis> These two
       deserve a place in <code>baseInputs</code> of
       <filename>autotools.nix</filename> as <command>findutils</command> and
       <command>patchelf</command>.

pills/10-developing-with-nix-shell.xml

@@ -129,11 +129,15 @@
     </para>
 
     <para>
-      The codebase is becoming a little long. You can find all the files in this
-      <link xlink:href="https://gist.github.com/lethalman/97fae227329b442267bc">nixpill10 gist</link>.
+      Here is our modified <filename>autotools.nix</filename>.
       Noteworthy is the <code>setup = ./setup.sh;</code> attribute in the
       derivation, which adds <filename>setup.sh</filename> to the nix store and
       as usual, adds a <code>$setup</code> environment variable in the builder.
+    </para>
+
+    <programlisting><xi:include href="./10/autotools-nix.txt" parse="text" /></programlisting>
+
+    <para>
       Thanks to that, we can split <filename>builder.sh</filename> into
       <filename>setup.sh</filename> and <filename>builder.sh</filename>. What
       <filename>builder.sh</filename> does is sourcing <code>$setup</code> and
@@ -141,6 +145,24 @@
       some bash changes.
     </para>
 
+    <para>
+      Here is the modified <filename>builder.sh</filename>.
+    </para>
+
+    <programlisting><xi:include href="./10/builder-sh.txt" parse="text" /></programlisting>
+
+    <para>
+      Here is the modified <filename>setup.sh</filename>.
+    </para>
+
+    <programlisting><xi:include href="./10/setup-sh.txt" parse="text" /></programlisting>
+
+    <para>
+      Finally, here is <filename>hello.nix</filename>.
+    </para>
+
+    <programlisting><xi:include href="./10/hello-nix.txt" parse="text" /></programlisting>
+
     <para>
       Now back to nix-shell:
     </para>

pills/10/autotools-nix.txt

@@ -0,0 +1,12 @@
+pkgs: attrs:
+  with pkgs;
+  let defaultAttrs = {
+    builder = "${bash}/bin/bash";
+    args = [ ./builder.sh ];
+    setup = ./setup.sh;
+    baseInputs = [ gnutar gzip gnumake gcc binutils-unwrapped coreutils gawk gnused gnugrep patchelf findutils ];
+    buildInputs = [];
+    system = builtins.currentSystem;
+  };
+  in
+derivation (defaultAttrs // attrs)

pills/10/builder-sh.txt

@@ -0,0 +1,3 @@
+set -e
+source $setup
+genericBuild

pills/10/hello-nix.txt

@@ -0,0 +1,7 @@
+let
+  pkgs = import <nixpkgs> {};
+  mkDerivation = import ./autotools.nix pkgs;
+in mkDerivation {
+  name = "hello";
+  src = ./hello-2.10.tar.gz;
+}

pills/10/setup-sh.txt

@@ -0,0 +1,39 @@
+unset PATH
+for p in $baseInputs $buildInputs; do
+  export PATH=$p/bin${PATH:+:}$PATH
+done
+
+function unpackPhase() {
+  tar -xzf $src
+
+  for d in *; do
+    if [ -d "$d" ]; then
+      cd "$d"
+      break
+    fi
+  done
+}
+
+function configurePhase() {
+  ./configure --prefix=$out
+}
+
+function buildPhase() {
+  make
+}
+
+function installPhase() {
+  make install
+}
+
+function fixupPhase() {
+  find $out -type f -exec patchelf --shrink-rpath '{}' \; -exec strip '{}' \; 2>/dev/null
+}
+
+function genericBuild() {
+  unpackPhase
+  configurePhase
+  buildPhase
+  installPhase
+  fixupPhase
+}