anchor.diff:  ----
   user=> (1 3 4) ; fails as it tries to invoke 1 as a function
   
  -ClassCastException java.lang.Long cannot be cast to clojure.lang.IFn  user/eval925 (NO_SOURCE_FILE:1)
  +Execution error (ClassCastException) at myproject.person-names/eval230 (REPL:1).
  +class java.lang.Long cannot be cast to class clojure.lang.IFn
  +
   user=> '(1 3 4) ; quote
   (1 3 4)
  +
   user=> (quote (1 2 3)) ; using the longer quote method
   (1 2 3)
   user=>
  
positive.code: user=> (defmacro m [] `(let [x 1] x))
  #'user/m
  user=> (m)
  CompilerException java.lang.RuntimeException: Can't let qualified name: user/x, compiling:(NO_SOURCE_PATH:1)
  ----
  
  This is because symbols inside a syntax quote are fully resolved, including the
  
negative.code: [source, clojure]
  ----
  user=> #{1 2 3 4 1}
  Syntax error reading source at (REPL:83:13).
  Duplicate key: 1
  ----
  
  * <<xref/../../reference/data_structures#sets,Clojure Documentation: Sets>>
  