r example, if the value was an integer, such as 
  <tt>42</tt>, it would be a <a href="http://clang.llvm.org/doxygen/classclang_1_1ento_1_1nonloc_1_1ConcreteInt.html">ConcreteInt</a>, 
  and the checker doesn't usually need to track any state with the concrete 
  number. In some cases, <tt>SVal</tt> is not a symbol, but it really should be 
  a symbolic value. This happens when the analyzer cannot reason about something 
  (yet). An example is floating point numbers. In such cases, the 
  <tt>SVal</tt> will