嗯,这显然是一个家庭作业问题,但无论如何,这里有一个 SWI Prolog 程序:
:- op(500, xfy, user:(+)).
simplify(Expr, Simplified) :-
split(Expr, Syms0, Nums0),
sumlist(Nums0, Nums),
append(Syms0, [Nums], Syms),
unparse(Syms, Simplified).
split(X+Y, [X|Syms], Nums) :- atom(X), split(Y, Syms, Nums).
split(X+Y, Syms, [X|Nums]) :- integer(X), split(Y, Syms, Nums).
split(X, [X], []) :- atom(X).
split(X, [], [X]) :- integer(X).
unparse([X], X).
unparse([X|Xs], X+Y) :- unparse(Xs, Y).
:- simplify(a+1+b+5, a+b+6).
:- simplify(1+b+9+a+5+c, b+a+c+15).