The Element API

Two APIs

The Rexx Parser defines two Application Programming Interfaces (APIs) to manipulate a parsed program, the Element API, described here, and the Tree API, described elsewhere. In some cases, it may be necessary to use both APIs might develop an application, but fairly sophisticated programs, like the Rexx Highlighter, can be written by resorting only to the Element API.

Elements

The Element API revolves around a very simple idea: the Rexx Parser provides a stream or chain of elements, implemented as a doubly linked list.

When a Rexx.Parser instance is created, the firstElement method can be called to obtain the first element in the stream. Error handling is considered in a separate article.

parser = .Rexx.Parser~new( name, source )    -- Instantiate a new parser
element  =  parser~firstElement              -- Get the first element

One then can progress from a element to the next one in the list by using the next method of the Element class.

Loop Until element == .Nil                   -- Loop over all elements in the list
  /* Process the element */                  -- Do something with this element
  element = element~next                     -- Get the next element, if it exists
End