Nullable nonterminals:

  (arg_list | arg_list_rest | concept_list_rest | equation_rest | exp_concat | 
  exp_concat_or_where | exp_var_or_func | pat_concat | pattern_list_rest | program_rest | 
  varassign_rest | variable_dec_rest | variable_list_rest)


The starters of nonterminals:

program ->
  (DEC)
program_rest ->
  (DEC)
function_dec ->
  (DEC)
var_dec_and_func_def ->
  (DEF | VAR)
variable_dec ->
  (VAR)
vars_decl ->
  (IDENTIFIER)
variable_dec_rest ->
  (IDENTIFIER)
variable_list ->
  (IDENTIFIER)
variable_list_rest ->
  (COMMA)
definition ->
  (DEF)
equation ->
  (IDENTIFIER)
equation_rest ->
  (IDENTIFIER)
pattern_list ->
  (IDENTIFIER | STRING)
pattern ->
  (IDENTIFIER | STRING)
pat_concat ->
  (CONCAT)
pattern_list_rest ->
  (COMMA)
function_type ->
  (IDENTIFIER)
concept_list_rest ->
  (ASTERISK)
concept_name ->
  (IDENTIFIER)
funname ->
  (IDENTIFIER)
variable ->
  (IDENTIFIER)
exp ->
  (IDENTIFIER | IF | LPAR | STRING)
exp_with_where ->
  (IDENTIFIER | IF | LPAR | STRING)
exp_with_where_or_undef ->
  (IDENTIFIER | IF | LPAR | STRING | UNDEFINED)
exp_var_or_func ->
  (LPAR)
arg_list ->
  (IDENTIFIER | IF | LPAR | STRING)
arg_list_rest ->
  (COMMA)
exp_concat ->
  (CONCAT)
exp_concat_or_where ->
  (CONCAT | WHERE)
varassign_list ->
  (IDENTIFIER)
varassign_rest ->
  (COMMA)


The followers of nullable nonterminals:

program_rest ->
  ($END)
variable_dec_rest ->
  (DEF)
variable_list_rest ->
  (COLON)
equation_rest ->
  ($END | DEC)
pat_concat ->
  (COMMA | RPAR)
pattern_list_rest ->
  (RPAR)
concept_list_rest ->
  (TO)
exp_var_or_func ->
  (COMMA | CONCAT | ELSE | RPAR | SC | 
  THEN | WHERE)
arg_list ->
  (RPAR)
arg_list_rest ->
  (RPAR)
exp_concat ->
  (COMMA | ELSE | RPAR | SC | THEN)
exp_concat_or_where ->
  (ELSE | RPAR | SC | THEN)
varassign_rest ->
  (ELSE | RPAR | SC | THEN)


*** Annotated grammar ***

program
: (DEC)
     function_dec var_dec_and_func_def #program_rest 
;

#program_rest
: ($END)
     /* empty */
| (DEC)
     program 
;

function_dec
: (DEC)
     DEC funname COLON function_type SC 
;

var_dec_and_func_def
: (VAR)
     variable_dec definition 
| (DEF)
     definition 
;

variable_dec
: (VAR)
     VAR vars_decl #variable_dec_rest 
;

vars_decl
: (IDENTIFIER)
     variable_list COLON concept_name SC 
;

#variable_dec_rest
: (DEF)
     /* empty */
| (IDENTIFIER)
     vars_decl #variable_dec_rest 
;

variable_list
: (IDENTIFIER)
     variable #variable_list_rest 
;

#variable_list_rest
: (COLON)
     /* empty */
| (COMMA)
     COMMA variable #variable_list_rest 
;

definition
: (DEF)
     DEF equation #equation_rest 
;

equation
: (IDENTIFIER)
     funname LPAR pattern_list RPAR EQ exp_with_where_or_undef SC 
;

#equation_rest
: ($END | DEC)
     /* empty */
| (IDENTIFIER)
     equation #equation_rest 
;

pattern_list
: (IDENTIFIER | STRING)
     pattern #pattern_list_rest 
;

pattern
: (STRING)
     STRING #pat_concat 
| (IDENTIFIER)
     variable #pat_concat 
;

#pat_concat
: (COMMA | RPAR)
     /* empty */
| (CONCAT)
     CONCAT pattern 
;

#pattern_list_rest
: (RPAR)
     /* empty */
| (COMMA)
     COMMA pattern #pattern_list_rest 
;

function_type
: (IDENTIFIER)
     concept_name #concept_list_rest TO concept_name 
;

#concept_list_rest
: (TO)
     /* empty */
| (ASTERISK)
     ASTERISK concept_name #concept_list_rest 
;

concept_name
: (IDENTIFIER)
     IDENTIFIER 
;

funname
: (IDENTIFIER)
     IDENTIFIER 
;

variable
: (IDENTIFIER)
     IDENTIFIER 
;

exp
: (STRING)
     STRING #exp_concat 
| (IDENTIFIER)
     IDENTIFIER #exp_var_or_func #exp_concat 
| (LPAR)
     LPAR exp_with_where RPAR #exp_concat 
| (IF)
     IF exp THEN exp ELSE exp 
;

exp_with_where
: (STRING)
     STRING #exp_concat_or_where 
| (IDENTIFIER)
     IDENTIFIER #exp_var_or_func #exp_concat_or_where 
| (LPAR)
     LPAR exp_with_where RPAR #exp_concat_or_where 
| (IF)
     IF exp_with_where THEN exp_with_where ELSE exp_with_where 
;

exp_with_where_or_undef
: (UNDEFINED)
     UNDEFINED 
| (IDENTIFIER | IF | LPAR | STRING)
     exp_with_where 
;

#exp_var_or_func
: (COMMA | CONCAT | ELSE | RPAR | SC | 
  THEN | WHERE)
     /* empty */
| (LPAR)
     LPAR #arg_list RPAR 
;

#arg_list
: (RPAR)
     /* empty */
| (IDENTIFIER | IF | LPAR | STRING)
     exp #arg_list_rest 
;

#arg_list_rest
: (RPAR)
     /* empty */
| (COMMA)
     COMMA exp #arg_list_rest 
;

#exp_concat
: (COMMA | ELSE | RPAR | SC | THEN)
     /* empty */
| (CONCAT)
     CONCAT exp 
;

#exp_concat_or_where
: (ELSE | RPAR | SC | THEN)
     /* empty */
| (CONCAT)
     CONCAT exp_with_where 
| (WHERE)
     WHERE varassign_list 
;

varassign_list
: (IDENTIFIER)
     variable EQ exp #varassign_rest 
;

#varassign_rest
: (ELSE | RPAR | SC | THEN)
     /* empty */
| (COMMA)
     COMMA varassign_list 
;