notes: add graphviz-based images

notes/20240930224229-concurrent_erlang.org

@@ -23,7 +23,7 @@ Pid = spawn(ModName, FuncName, [Arg1, Arg2, ..., ArgN]).
     sep = 1;
 
     pid1 [label="Pid 1", fontsize="10pt", style=filled, fillcolor=grey];
-    pid2 [label="Pid 2", xlabel="Mod:Func(Args)", fontsize="10pt", style=filled, fillcolor=red];
+    pid2 [label="Pid 2", xlabel="Mod:Func(Args)", fontsize="10pt", style=filled, fillcolor=white];
 
     pid1 -> pid2 [label="  Spawn(Mod, Func, Args)", fontsize="10pt", minlen=1, style=dashed];
   }
@@ -46,7 +46,7 @@ Pid = spawn(ModName, FuncName, [Arg1, Arg2, ..., ArgN]).
     rankdir="LR";
 
     pid1 [label="Pid 1", xlabel="Pid2 ! { self(), hello }", fontsize="10pt", style=filled, fillcolor=grey];
-    pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=red, xlabel="receive (...) end." ];
+    pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=white, xlabel="receive (...) end." ];
 
     pid1 -> pid2 [label="{ Pid1, hello }", fontsize="10pt", style=dashed];
   }
@@ -91,7 +91,7 @@ end
 
           pid1 [label="Pid 1", xlabel="Pid 3 ! { foo, ... }", fontsize="10pt", style=filled, fillcolor=grey];
           pid2 [label="Pid 2", xlabel="Pid 3 ! { bar, ... }", fontsize="10pt", style=filled, fillcolor=grey];
-          pid3 [label="Pid 3", fontsize="10pt", style=filled, fillcolor=red];
+          pid3 [label="Pid 3", fontsize="10pt", style=filled, fillcolor=white];
 
           pid1 -> pid3 [label="{foo, ...}", fontsize="10pt", minlen=1, style=dashed];
           pid2 -> pid3 [label="{bar, ...}", fontsize="10pt", minlen=1, style=dashed];
@@ -144,7 +144,7 @@ end
 
       timeout [label="🕒", fontsize="10pt", style=filled, fillcolor=white];
       pid1 [label="Pid 1", fontsize="10pt", style=filled, fillcolor=grey];
-      pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=red];
+      pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=grey];
 
       timeout -> pid2 [label="Timeout", fontsize="10pt", minlen=1, style=dashed];
       pid1 -> pid2 [label="Msg", fontsize="10pt", minlen=1, style=dashed];

notes/20241001192402-error_handling_in_erlang.org

@@ -56,7 +56,7 @@ P3.
       rankdir="LR";
       sep = 1;
 
-      pid1 [label="Pid 1", fontsize="10pt", style=filled, fontcolor=white; fillcolor=black];
+      pid1 [label="Pid 1", fontsize="10pt", style=filled, fillcolor=red];
       pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=grey];
 
       pid1 -> pid2 [label="{'Exit', Pid1, Reason}", dir=both, fontsize="10pt", minlen=1, style=dashed];
@@ -80,7 +80,7 @@ P3.
       rankdir="LR";
       sep = 1;
 
-      pid1 [label="Pid 1", fontsize="10pt", style=filled, fontcolor=white; fillcolor=black];
+      pid1 [label="Pid 1", fontsize="10pt", style=filled, fillcolor=red];
       pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=grey; shape=doublecircle];
       pid3 [label="Pid 3", fontsize="10pt", style=filled, fillcolor=grey];
 
@@ -93,4 +93,24 @@ P3.
 #+RESULTS: erlang-error-trapping
 [[file:../static/img/notes/erlang_error_trapping.png]]
 
+#+NAME: erlang-error-propagation
+#+BEGIN_SRC dot :file ../static/img/notes/erlang_error_propagation.png :cmdline -Kdot -Tpng :exports results
+  digraph Trapping {
+      node [shape=circle];
+      rankdir="LR";
+      sep = 1;
+
+      pid1 [label="Pid 1", fontsize="10pt", style=filled, fillcolor=red];
+      pid2 [label="Pid 2", fontsize="10pt", style=filled, fillcolor=grey; shape=doublecircle];
+      pid3 [label="Pid 3", fontsize="10pt", style=filled, fillcolor=grey];
+
+
+      pid1 -> pid2 [label="{'Exit', Pid1, Reason}", dir=both, fontsize="10pt", minlen=1, style=dashed];
+      pid2 -> pid3 [dir=both, fontsize="10pt", minlen=2, style=dashed];
+  }
+#+END_SRC
+
+#+RESULTS: erlang-error-propagation
+[[file:../static/img/notes/erlang_error_propagation.png]]
+
 #+print_bibliography:

notes/20241004123538-erlang_shell.org

@@ -7,7 +7,7 @@
 
 Some features of the [[id:de7d0e94-618f-4982-b3e5-8806d88cad5d][Erlang]] shell.
 
-* Examples
+* Basics
 ** Compiling and Running "Hello World" in the Shell
 #+BEGIN_SRC erlang
   -module(hello).
@@ -64,4 +64,22 @@ terminates the Erlang session. [cite:@armstrong2013 p.14]
   > f().
 #+END_SRC
 
+* Modifying the Development Environment
+
+You can find the value of the current load path by starting an Erlang shell
+and giving the command ~code:get_path()~. The two most common functions that we
+use to manipulate the load path are as follows:
+
+#+begin_src erlang
+% Add a new directory to the start of the load path.
+-spec code:add_patha(Dir) => true | {error, bad_directory}
+% Add a new directory to the end of the load path.
+-spec code:add_pathz(Dir) => true | {error, bad_directory}
+#+end_src
+
+Alternatively, you can start Erlang with a command like this:
+#+begin_src shell
+$ erl -pa Dir1 -pa Dir2 ... -pz DirK1 -pz DirK2
+#+end_src
+
 #+print_bibliography:

notes/20241009092203-dializer.org

@@ -36,17 +36,44 @@ Tuple :: tuple() | {T1, T2, ... Tn}
 #+END_SRC
 
 New types can be defined with the following syntax:
-#+begin_src 
+#+begin_src erlang
   -type NewTypeName(TVar1, TVar2, ... , TVarN) :: Type.
 #+end_src
 
 ** Specifying the Input and Output Types of a Function
 
-#+BEGIN_SRC 
+#+BEGIN_SRC erlang
 -spec file:open(FileName, Modes) -> {ok, Handle} | {error, Why} when
     FileName :: string(),
     Modes :: [Mode],
     Mode :: read | write | ...
     Handle :: file_handle(),
     Why :: error_term().
 #+END_SRC
+
+** Exporting Types
+A module can export some types to declare that other modules are allowed to
+refer to them as remote types. This declaration has the following form:
+
+#+BEGIN_SRC erlang
+  -export_type([T1/A1, ..., Tk/Ak]).
+#+END_SRC
+
+** Opaque Types
+The main use case for opacity in Erlang is to hide the implementation of a data
+type, enabling evolving the API while minimizing the risk of breaking consumers.
+
+* Running Dializer
+** Things that confuse Dializer
+The dialyzer can get easily confused. We can help prevent this by following a
+few simple rules. [cite:@armstrong2013 p.151].
++ Avoid using ~-compile(export_all)~.
++ Provide detailed type specifications for all the arguments to the *exported*
+  functions in the module.
++ Provide default arguments to all elements in a record definition. If you don't
+  provide a default, the atom ~undefined~ is taken as the default.
++ Using anonymous variables in arguments to a function often results in types
+  that are far less specific than you had intended; try to constrain variables
+  as much as possible.
+
+#+print_bibliography: