lily/language.grammar

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token whitespace = /[ \n\t]+/ [ skip ];
token upper_identifier = /[A-Z_][a-z_A-Z0-9]*/;
token lower_identifier = /[a-z_][a-z_A-Z0-9]*/;
token number = /[0-9]+/;
token kw_data = /data/;
token kw_type = /type/;
token kw_defn = /defn/;
token kw_let = /let/;
token kw_letrec = /letrec/;
token kw_in = /in/;
token kw_case = /case/;
token kw_of = /of/;
token tkn_ocurly = /{/;
token tkn_ccurly = /}/;
token tkn_oparen = /\(/;
token tkn_cparen = /\)/;
token tkn_eq = /=/;
token tkn_comma = /,/;
token tkn_arrow = /->/;
token op_add = /\+/;
token op_sub = /-/;
token op_mul = /\*/;
token op_div = /\//;
rule S = program;
rule program
= definition program?
;
rule definition
= kw_data upper_identifier tkn_eq data_body
| kw_type upper_identifier tkn_eq type_body
| kw_defn lower_identifier params? tkn_eq defn_body
;
rule data_body
= tkn_ocurly data_elems tkn_ccurly
;
rule data_elems
= data_elem
| data_elem tkn_comma data_elems
;
rule data_elem
= upper_identifier
| upper_identifier tkn_oparen data_elem_types tkn_cparen
;
rule data_elem_types
= type
| type tkn_comma data_elem_types
;
rule type_body
= tkn_ocurly type tkn_ccurly
;
rule params
= lower_identifier params?
;
rule defn_body
= tkn_ocurly expr tkn_ccurly
;
rule expr
= expr_add
| expr_let
| expr_letrec
| expr_case
;
rule expr_add
= expr_add op_add expr_mul
| expr_add op_sub expr_mul
| expr_mul
;
rule expr_mul
= expr_mul op_mul expr_app
| expr_mul op_div expr_app
| expr_app
;
rule expr_app
= expr_app? expr_app_bottom
;
rule expr_app_bottom
= lower_identifier
| upper_identifier
| number
| tkn_oparen expr tkn_cparen
;
rule expr_curly
= tkn_ocurly expr tkn_ccurly
;
rule expr_let
= kw_let lower_identifier tkn_eq expr_curly kw_in expr_curly
;
rule expr_letrec
= kw_letrec lower_identifier tkn_eq expr_curly kw_in expr_curly
;
rule expr_case
= kw_case expr kw_of tkn_ocurly expr_case_branches tkn_ccurly
;
rule expr_case_branches
= expr_case_branch expr_case_branches?
;
rule expr_case_branch
= pattern tkn_arrow expr_curly
;
rule pattern
= lower_identifier
| upper_identifier
| upper_identifier tkn_oparen patterns tkn_cparen
;
rule patterns
= lower_identifier
| lower_identifier tkn_comma patterns
;
rule type
= upper_identifier
;