Move string manipulation FAQ items to type docs

Update docs/types/value-types.rst

Co-Authored-By: ChrisChinchilla <chriswhward@gmail.com>

Update docs/types/value-types.rst

Co-Authored-By: ChrisChinchilla <chriswhward@gmail.com>

Fixed formatting

Re-add example

Clarify text

Rearrange string manipulation

docs/control-structures.rst

@@ -264,13 +264,13 @@ Complications for Arrays and Structs
 The semantics of assignments are a bit more complicated for non-value types like arrays and structs.
 Assigning *to* a state variable always creates an independent copy. On the other hand, assigning to a local variable creates an independent copy only for elementary types, i.e. static types that fit into 32 bytes. If structs or arrays (including ``bytes`` and ``string``) are assigned from a state variable to a local variable, the local variable holds a reference to the original state variable. A second assignment to the local variable does not modify the state but only changes the reference. Assignments to members (or elements) of the local variable *do* change the state.
 
-In the example below the call to ``g(x)`` has no effect on ``x`` because it needs
+In the example below the call to ``g(x)`` has no effect on ``x`` because it creates
-to create an independent copy of the storage value in memory. However ``h(x)`` modifies ``x`` because a reference and
+an independent copy of the storage value in memory. However, ``h(x)`` successfully modifies ``x``
-not a copy is passed.
+because only a reference and not a copy is passed.
 
 ::
 
-     pragma solidity >=0.4.16 <0.6.0;
+    pragma solidity >=0.4.16 <0.6.0;
 
      contract C {
         uint[20] x;

docs/frequently-asked-questions.rst

@@ -16,44 +16,6 @@ Enums are not supported by the ABI, they are just supported by Solidity.
 You have to do the mapping yourself for now, we might provide some help
 later.
 
-What are some examples of basic string manipulation (``substring``, ``indexOf``, ``charAt``, etc)?
-==================================================================================================
-
-There are some string utility functions at `stringUtils.sol <https://github.com/ethereum/dapp-bin/blob/master/library/stringUtils.sol>`_
-which will be extended in the future. In addition, Arachnid has written `solidity-stringutils <https://github.com/Arachnid/solidity-stringutils>`_.
-
-For now, if you want to modify a string (even when you only want to know its length),
-you should always convert it to a ``bytes`` first::
-
-    pragma solidity >=0.4.0 <0.6.0;
-
-    contract C {
-        string s;
-
-        function append(byte c) public {
-            bytes(s).push(c);
-        }
-
-        function set(uint i, byte c) public {
-            bytes(s)[i] = c;
-        }
-    }
-
-
-Can I concatenate two strings?
-==============================
-
-Yes, you can use ``abi.encodePacked``::
-
-    pragma solidity >=0.4.0 <0.6.0;
-
-    library ConcatHelper {
-        function concat(bytes memory a, bytes memory b)
-                internal pure returns (bytes memory) {
-            return abi.encodePacked(a, b);
-        }
-    }
-
 ******************
 Advanced Questions
 ******************

docs/types/reference-types.rst

@@ -106,13 +106,24 @@ Array elements can be of any type, including mapping or struct. The general
 restrictions for types apply, in that mappings can only be stored in the
 ``storage`` data location and publicly-visible functions need parameters that are :ref:`ABI types <ABI>`.
 
+It is possible to mark arrays ``public`` and have Solidity create a :ref:`getter <visibility-and-getters>`.
+The numeric index becomes a required parameter for the getter.
+
 Accessing an array past its end causes a failing assertion. You can use the ``.push()`` method to append a new element at the end or assign to the ``.length`` :ref:`member <array-members>` to change the size (see below for caveats).
 method or increase the ``.length`` :ref:`member <array-members>` to add elements.
 
+``bytes`` and ``strings`` as Arrays
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 Variables of type ``bytes`` and ``string`` are special arrays. A ``bytes`` is similar to ``byte[]``,
 but it is packed tightly in calldata and memory. ``string`` is equal to ``bytes`` but does not allow
 length or index access.
 
+While Solidity does not have string manipulation functions, you can use
+this implicit conversion for equivalent functionality. For example to compare
+two strings ``keccak256(abi.encode(s1)) == keccak256(abi.encode(s2))``, or to
+concatenate two strings already encoded with ``abi.encodePacked(s1, s2);``.
+
 You should use ``bytes`` over ``byte[]`` because it is cheaper, since ``byte[]`` adds 31 padding bytes between the elements. As a general rule,
 use ``bytes`` for arbitrary-length raw byte data and ``string`` for arbitrary-length
 string (UTF-8) data. If you can limit the length to a certain number of bytes,
@@ -124,9 +135,6 @@ always use one of the value types ``bytes1`` to ``bytes32`` because they are muc
     that you are accessing the low-level bytes of the UTF-8 representation,
     and not the individual characters.
 
-It is possible to mark arrays ``public`` and have Solidity create a :ref:`getter <visibility-and-getters>`.
-The numeric index becomes a required parameter for the getter.
-
 .. index:: ! array;allocating, new
 
 Allocating Memory Arrays