Added language basics section.

user_guide/source/index.rst

@@ -7,11 +7,12 @@ The Obsidian Smart Contract Language
 ======================================
 
 .. toctree::
-   :maxdepth: 1
+   :maxdepth: 2
    :hidden:
 
    Getting Started <getting_started>
    Obsidian Language Tutorial <tutorial/tutorial>
+   Obsidian Reference <reference/reference>
    Contributing to Obsidian <contributing>
 
 

user_guide/source/reference/basics.rst

@@ -0,0 +1,25 @@
+Obsidian Language Basics
+==========================
+
+Contracts, transactions, and main contracts
+----------------------------------------------
+Obsidian is object-oriented. A ``contract`` is like a class: it can be instantiated as many times as needed. Each contract supports operations; each one is called a ``transaction``. Transactions are akin to methods in traditional object-oriented languages. However, unlike methods, transactions either completely finish or revert. If a transaction reverts (via the ``revert`` statement), then all changes that the transaction made will be discarded.
+
+Main contracts
+-----------------
+A ``main`` contract may be instantiated on the blockchain. The contract's transactions are then available for clients to invoke. Only ``main`` contracts can be deployed directly, and the Obsidian compiler expects every program to have one ``main`` contract.
+
+Constructors
+------------
+Constructors must initialize all the fields of their contracts. In addition, construtors of contracts that have defined states must transition the object to a particular state. It is good practice for constructors to specify a specific state that the object will be in if possible; otherwise, generally you should declare constructors to return an ``Owned`` reference. For example:
+
+::
+
+   contract LightSwitch {
+      state On;
+      state Off;
+
+      LightSwitch@Off() { // the resulting object will be in Off state 
+         ->Off;
+      }
+   }

user_guide/source/reference/reference.rst

@@ -0,0 +1,7 @@
+Obsidian Language Reference
+============================
+
+Before using this reference guide, please read the entire tutorial first, since the reference guide uses concepts explained in the tutorial.
+
+.. toctree::
+   Language Basics <basics>