anchor.diff:  :marked
     <a id="pipe"></a>
     ### The pipe operator ( | )
  +  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 these.
     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 (`|`)**:
  +  They're 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.
  
positive.code:     The `json` pipe is particularly helpful for debugging our bindings:
    +makeExample('template-syntax/ts/app/app.component.html', 'pipes-json')(format=".")
    :marked
      The generated output would look something like this:
    code-example(language="json").
      { "firstName": "Hercules", "lastName": "Son of Zeus",
        "birthdate": "1970-02-25T08:00:00.000Z",
  
negative.code:   ### 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, 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
  