%   ORIGINAL: 'h4/thm/list/NULL_LENGTH_'
% Assm: HL_TRUTH: T
% Assm: HL_FALSITY: ~F
% Assm: HL_BOOL_CASES: !t. (t <=> T) \/ (t <=> F)
% Assm: HL_EXT: !f g. (!x. f x = g x) ==> f = g
% Goal: !l. 'h4/const/list/NULL' l <=> 'h4/const/list/LENGTH' l = 'h4/const/num/0'
%   PROCESSED
% Assm ['HL_TRUTH']: T
% Assm ['HL_FALSITY']: ~F
% Assm ['HL_BOOL_CASES']: !t. (t <=> T) \/ (t <=> F)
% Assm ['HL_EXT']: !f g. (!x. happ f x = happ g x) ==> f = g
% Goal: !l. 'h4/const/list/NULL' l <=> 'h4/const/list/LENGTH' l = 'h4/const/num/0'
fof('HL_TRUTH', axiom, p(s(bool,'T'))).
fof('HL_FALSITY', axiom, ~ (p(s(bool,'F')))).
fof('HL_BOOL_CASES', axiom, ![T]: (s(bool,T) = s(bool,'T') | s(bool,T) = s(bool,'F'))).
fof('HL_EXT', axiom, ![V_3f4063,V_3f4059]: ![F, G]: (![X]: s(V_3f4059,happ(s(fun(V_3f4063,V_3f4059),F),s(V_3f4063,X))) = s(V_3f4059,happ(s(fun(V_3f4063,V_3f4059),G),s(V_3f4063,X))) => s(fun(V_3f4063,V_3f4059),F) = s(fun(V_3f4063,V_3f4059),G))).
fof('h4/thm/list/NULL_LENGTH_', conjecture, ![A]: ![L]: (p(s(bool,'h4/const/list/NULL'(s('h4/type/list/list'(A),L)))) <=> s('h4/type/num/num','h4/const/list/LENGTH'(s('h4/type/list/list'(A),L))) = s('h4/type/num/num','h4/const/num/0'))).
