%token ID COMMA COLON 

%%

def:
      param_spec return_spec COMMA 
;
param_spec:
      type
    | name_list COLON type 
;
return_spec:
      type
    | ID COLON type 
;
type:
      ID 
;
name:
      ID 
;
name_list:
      name
    | name COMMA name_list 
;

%%