The Parser Projection

Freon generates a parser (wrapped in a file reader), and un unparser (wrapped in a file writer), both based on the default projection. Because the unparser must be able to read the files that were written using the parser, both are based on the same projection.

However, if the default projection is not suitable for reading from or writing to text files, a separate projection called parser can be used. This projection is never shown in the editor. Like other projections, the parser generation falls back to the default projection for a certain concept, when no definition is present in the parser projection set.

Layout elements, such as vertical and horizontal lists, are preserved wherever possible. Furthermore, typical parse problems like left and right recursion are avoided. To be able to do so, Freon uses a parser generator called AGL, created by David Akehurst, which is more powerful than most PEG parser generators.

However, it is still possible to create a projection that cannot be parsed. Please consider this when writing the parser projection.