ebnf.eag

// This EAG shows the use of EBNF expressions for group, option, and repetition
// with corresponding parameters.
// The meaning is defined by the lowering in the related example/bnf/ebnf.eag.

S = S ',' S | L.

S <+ L1 ',' L2 ',' L3: S>:
    Group <L1> ',' Option <L2> ',' Repetition <L3>
  | GroupSubrule <L1> ',' OptionSubrule <L2> ',' RepetitionSubrule <L3>.

L = 'a' L | 'b' L | .

Group:
    ( <+ 'a': L> 'a'
    | <+ 'b': L> 'b'
    ).

Option:
    [ <+ 'a': L> 'a'
    | <+ 'b': L> 'b'
    ] <+ : L>.

Repetition:
    { <+ 'a' L: L> 'a' <L>
    | <+ 'b' L: L> 'b' <L>
    } <+ : L>.

GroupSubrule <+ L>:
    '"'
    <L>
        ( <+ 'a': L> 'a'
        | <+ 'b': L> 'b'
        )
    '"'.

OptionSubrule <+ L>:
    '"'
    <L>
        [ <+ 'a': L> 'a'
        | <+ 'a': L> 'b'
        ] <+ : L>
    '"'.

RepetitionSubrule <+L>:
    '"'
    <L>
        { <+ 'a' L: L> 'a' <L>
        | <+ 'b' L: L> 'b' <L>
        } <+ : L>
    '"'.