anchor.diff:    ### The safe navigation operator ( ?. ) and null property paths
   
     The Angular **safe navigation operator (`?.`)** is a fluent and convenient way to guard against null and undefined values in property paths.
  -  Here it is used to protect against against a view render failure if the `currentHero` is null:
  +  Here it is, protecting against a view render failure if the `currentHero` is null.
   +makeExample('template-syntax/ts/app/app.component.html', 'safe-2')(format=".")
   
   block dart-safe-nav-op
  
positive.code: :marked
    <a id="pipe"></a>
    ### The pipe operator ( | )
    Pipes are simple functions that accept an input value and return a transformed value.
    The result of an expression might require some transformation before we’re ready to use it in a binding.  For example, we might want to display a number as a currency, force text to uppercase, or filter a list and sort it.
  
    Angular [pipes](./pipes.html) are a good choice for small transformations such as those listed above.
    Pipe operators are easy to apply within template expressions, using the **pipe operator (`|`)**:
  +makeExample('template-syntax/ts/app/app.component.html', 'pipes-1')(format=".")
  :marked
    The pipe operator passes the result of an expression on the left to a pipe function on the right.
  
negative.code:   We can chain expressions through multiple pipes:
  +makeExample('template-syntax/ts/app/app.component.html', 'pipes-2')(format=".")
  :marked
    And we can also [apply parameters](./pipes.html#parameterizing-a-pipe) to a pipe:
  +makeExample('template-syntax/ts/app/app.component.html', 'pipes-3')(format=".")
  
  block json-pipe
  