 // MARK: RenderFunction
 
 /**
-RenderFunction lets you implement custom rendering functions. This is how, for
-example, you implement "lambdas", in Mustache lingo.
-
-Sections and variable tags can be attached to custom render functions:
+A RenderFunction is invoked as soon as a variable tag {{name}} or a section
+tag {{#name}}...{{/name}} is rendered, and lets you implement custom rendering.
+
+This is how, for example, you implement "Mustache lambdas".
 
 ::
 

  }
  

  Note how the spec, mustache.js and Ruby mustache require a double parsing of
  the inner content of the section: they all process a String containing the
  unprocessed section contents.

  There is a better way to write this lambda, by wrapping the rendering of the
  already-parsed Mustache tag:

  // The strong RenderFunction below is equivalent to this Handlebars.js helper:
  //

      return Rendering("foo")
  }
  
  // A template that contains both a section and a variable tag:
  let template = Template(string: "{{#section}}variable: {{variable}}{{/section}}")!
  
  // Attach the render function to `variable`: render "variable: foo"
  let data1 = ["section": Box(["variable": Box(render)])]
  let rendering1 = template.render(Box(data1))!

  // Attach the render function to `section`: render "foo"
  let data2 = ["section": Box(render)]
  let rendering2 = template.render(Box(data2))!


The Mustache specification defines lambdas at
https://github.com/mustache/spec/blob/master/specs/%7Elambdas.yml:
