% Uebung 11
%
% a) Parser
%

pair(X,Y,(X,Y)).

char_atom(C,A) :-
   maplist(pair, "CHNOPS", [c,h,n,o,p,s], CAs),
   member((C,A),CAs).

is_digit_code(X) :- code_type(X,digit).

text_number(1,[]).
text_number(N,[D|Ds]) :- number_codes(N,[D|Ds]).

text_formula([],[]).
text_formula([C|Cs],[(A,N)|S]) :-
   char_atom(C,A),
   append(NS,R,Cs),
   maplist(is_digit_code, NS),
   text_number(N,NS),
   text_formula(R,S).