Merge pull request #5755 from ethereum/docs-split-using-for

[DOCS] Split using for into new file

1 files changed, 1 insertions, 119 deletions

diff --git a/docs/contracts.rst b/docs/contracts.rst
index 7f7d821a..f72707cb 100644
--- a/docs/contracts.rst
+++ b/docs/contracts.rst
@@ -803,122 +803,4 @@ constant to be pushed onto the stack and the dispatcher
 code compares the current address against this constant
 for any non-view and non-pure function.
 
-.. index:: ! using for, library
-
-.. _using-for:
-
-*********
-Using For
-*********
-
-The directive ``using A for B;`` can be used to attach library
-functions (from the library ``A``) to any type (``B``).
-These functions will receive the object they are called on
-as their first parameter (like the ``self`` variable in Python).
-
-The effect of ``using A for *;`` is that the functions from
-the library ``A`` are attached to *any* type.
-
-In both situations, *all* functions in the library are attached,
-even those where the type of the first parameter does not
-match the type of the object. The type is checked at the
-point the function is called and function overload
-resolution is performed.
-
-The ``using A for B;`` directive is active only within the current
-contract, including within all of its functions, and has no effect
-outside of the contract in which it is used. The directive
-may only be used inside a contract, not inside any of its functions.
-
-By including a library, its data types including library functions are
-available without having to add further code.
-
-Let us rewrite the set example from the
-:ref:`libraries` in this way::
-
-    pragma solidity >=0.4.16 <0.6.0;
-
-    // This is the same code as before, just without comments
-    library Set {
-      struct Data { mapping(uint => bool) flags; }
-
-      function insert(Data storage self, uint value)
-          public
-          returns (bool)
-      {
-          if (self.flags[value])
-            return false; // already there
-          self.flags[value] = true;
-          return true;
-      }
-
-      function remove(Data storage self, uint value)
-          public
-          returns (bool)
-      {
-          if (!self.flags[value])
-              return false; // not there
-          self.flags[value] = false;
-          return true;
-      }
-
-      function contains(Data storage self, uint value)
-          public
-          view
-          returns (bool)
-      {
-          return self.flags[value];
-      }
-    }
-
-    contract C {
-        using Set for Set.Data; // this is the crucial change
-        Set.Data knownValues;
-
-        function register(uint value) public {
-            // Here, all variables of type Set.Data have
-            // corresponding member functions.
-            // The following function call is identical to
-            // `Set.insert(knownValues, value)`
-            require(knownValues.insert(value));
-        }
-    }
-
-It is also possible to extend elementary types in that way::
-
-    pragma solidity >=0.4.16 <0.6.0;
-
-    library Search {
-        function indexOf(uint[] storage self, uint value)
-            public
-            view
-            returns (uint)
-        {
-            for (uint i = 0; i < self.length; i++)
-                if (self[i] == value) return i;
-            return uint(-1);
-        }
-    }
-
-    contract C {
-        using Search for uint[];
-        uint[] data;
-
-        function append(uint value) public {
-            data.push(value);
-        }
-
-        function replace(uint _old, uint _new) public {
-            // This performs the library function call
-            uint index = data.indexOf(_old);
-            if (index == uint(-1))
-                data.push(_new);
-            else
-                data[index] = _new;
-        }
-    }
-
-Note that all library calls are actual EVM function calls. This means that
-if you pass memory or value types, a copy will be performed, even of the
-``self`` variable. The only situation where no copy will be performed
-is when storage reference variables are used.
+.. include:: contracts/using-for.rst
\ No newline at end of file