Document pure functions

docs/contracts.rst

@@ -475,7 +475,7 @@ Functions can be declared ``view`` in which case they promise not to modify the
 
     contract C {
         function f(uint a, uint b) view returns (uint) {
-            return a * (b + 42);
+            return a * (b + 42) + now;
         }
     }
 
@@ -488,6 +488,27 @@ Functions can be declared ``view`` in which case they promise not to modify the
 .. warning::
   The compiler does not enforce yet that a ``view`` method is not modifying state.
 
+.. _pure-functions:
+
+**************
+Pure Functions
+**************
+
+Functions can be declared ``pure`` in which case they promise not to read from or modify the state.
+
+::
+
+    pragma solidity ^0.4.0;
+
+    contract C {
+        function f(uint a, uint b) pure returns (uint) {
+            return a * (b + 42);
+        }
+    }
+
+.. warning::
+  The compiler does not enforce yet that a ``pure`` method is not reading from the state.
+
 .. index:: ! fallback function, function;fallback
 
 .. _fallback-function:

docs/miscellaneous.rst

@@ -500,12 +500,13 @@ Function Visibility Specifiers
 - ``internal``: only visible internally
 
 
-.. index:: modifiers, constant, anonymous, indexed
+.. index:: modifiers, pure, view, payable, constant, anonymous, indexed
 
 Modifiers
 =========
 
-- ``view`` for functions: Disallow modification of state - this is not enforced yet.
+- ``pure`` for functions: Disallows modification or access of state - this is not enforced yet.
+- ``view`` for functions: Disallows modification of state - this is not enforced yet.
 - ``payable`` for functions: Allows them to receive Ether together with a call.
 - ``constant`` for state variables: Disallows assignment (except initialisation), does not occupy storage slot.
 - ``constant`` for functions: Same as ``view``.