Document constant functions

1 files changed, 24 insertions, 3 deletions

diff --git a/docs/contracts.rst b/docs/contracts.rst
index 986d05b3..e2fdf3f3 100644
--- a/docs/contracts.rst
+++ b/docs/contracts.rst
@@ -421,9 +421,9 @@ change by overriding).
 
 .. index:: ! constant
 
-**********
-Constants
-**********
+************************
+Constant State Variables
+************************
 
 State variables can be declared as constant (this is not yet implemented
 for array and struct types and not possible for mapping types).
@@ -442,6 +442,27 @@ for these variables and every occurrence is replaced by their constant value.
 
 The value expression can only contain integer arithmetics.
 
+******************
+Constant Functions
+******************
+
+Functions can be declared constant. These functions promise not to modify the state.
+
+::
+
+    pragma solidity ^0.4.0;
+
+    contract C {
+        function f(uint a, uint b) constant returns (uint) {
+            return a * (b + 42);
+        }
+    }
+
+.. note::
+  Accessor methods are marked constant.
+
+.. warning::
+  The compiler does not enforce yet that a constant method is not modifying state.
 
 .. index:: ! fallback function, function;fallback