Begin language doc [ci-skip]

doc/userdoc.org

@@ -395,16 +395,36 @@ write errors.
 
 * Language
 
-In this part we describe the grammar and data types that are
-
 ** Variables
 
-*** TODO Declaration
+In order to simplify the presentation, before going further, we
+introduce the construction that allow to print data to the
+terminal. It follows ~C++~ streams construction for convenience. For
+instance
+#+NAME: cout-preamble-example
+#+BEGIN_SRC pugs :exports both :results output
+  cout << "2+3 = " << 2+3 << "\n";
+#+END_SRC
+produces the following output
+#+results: cout-preamble-example
+The code is quite obvious for ~C++~ users, note that ~"\n"~ is the
+linefeed string (there is no character type in ~pugs~, just strings).
+
+Actually, ~cout~ is itself a variable, we will come to this later.
 
-*** TODO Affectation
+~pugs~ is a strongly typed language. It means that a variable *cannot*
+change of type in its lifetime.
 
 *** TODO Basic types<<basic-types>>
 
+Basic types in ~pugs~ are boolean ~B~, natural integers ~N~, integers ~Z~,
+real ~R~, small vectors ~R^1~, ~R^2~ and ~R^3~, small matrices ~R^1x1~, ~R^2x2~
+and ~R^3x3~ and strings ~string~.
+
+
+
+*** TODO Declaration and affectation syntax
+
 *** TODO High-level types<<high-level-types>>
 
 *** TODO Lists