Add basic language grammar (without expressions)

language.grammar

@@ -0,0 +1,63 @@
+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 kw_data = /data/;
+token kw_type = /type/;
+token kw_defn = /defn/;
+token tkn_ocurly = /{/;
+token tkn_ccurly = /}/;
+token tkn_oparen = /\(/;
+token tkn_cparen = /\)/;
+token tkn_eq = /=/;
+token tkn_comma = /,/;
+
+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
+    = lower_identifier
+    ;
+
+rule type
+    = upper_identifier
+    ;