Modernize code:

* Clean STBase-derived class creation interfaces
* Annotate overriden STBase virtual functions
* Optimize path deserialization
* Prefer range-based for
* Prefer std::unique_ptr
* Remove BOOST_FOREACH

src/ripple/protocol/impl/STAmount.cpp

@@ -28,6 +28,8 @@
 #include <boost/regex.hpp>
 #include <boost/algorithm/string.hpp>
 #include <beast/cxx14/iterator.h> // <iterator>
+#include <beast/cxx14/memory.h> // <memory>
+#include <iostream>
 
 namespace ripple {
 
@@ -35,6 +37,9 @@ static const std::uint64_t tenTo14 = 100000000000000ull;
 static const std::uint64_t tenTo14m1 = tenTo14 - 1;
 static const std::uint64_t tenTo17 = tenTo14 * 1000;
 
+STAmount const saZero (noIssue(), 0u);
+STAmount const saOne (noIssue(), 1u);
+
 //------------------------------------------------------------------------------
 
 STAmount::STAmount (SField::ref name, Issue const& issue,
@@ -494,14 +499,6 @@ std::string STAmount::getHumanCurrency () const
     return to_string (mIssue.currency);
 }
 
-void
-STAmount::setNValue (std::uint64_t v)
-{
-    if (!mIsNative)
-        throw std::runtime_error ("not native");
-    mValue = v;
-}
-
 void
 STAmount::setSNValue (std::int64_t v)
 {
@@ -752,12 +749,6 @@ STAmount::isEquivalent (const STBase& t) const
     return v && (*v == *this);
 }
 
-STAmount*
-STAmount::duplicate () const
-{
-    return new STAmount (*this);
-}
-
 //------------------------------------------------------------------------------
 
 // amount = value * [10 ^ offset]