Parser DDSL¶

Fan’s parser DDSL is fully self-explainable, its runtime has enough meta-data to reconstruct itself.

Learn the syntax by yourself

Suppose you have toplevel installed successfully ( see Toplevel support).
```
$ #directory "+fan";;
$ #load "fanTop.cma";;
```
Now if you want to understand what’s the definition for the syntactic category case
```
Fgram.print Format.std_formatter Fsyntax.case ;;
```
The output is something like this:
```
case:
  [ LA
  [ "|"; L1 case0 SEP "|" -> bar_of_list l
  | pat; "->"; exp -> `Case (_loc, p, e)]
  ]
```
Unlike Camlp4, such grammar printer is the original grammar which is 100% honest to the user’s input, no computation involved.

So you can install the printer in the toplevel and explore different non-terminals by your self.
```
$ #install_printer Fgram.print;;
```

Todo

How the parser works
Where is the lexer?
TODO Functional generation