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A simple demo of type inference in SWI-Prolog
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| :- initialization(main). | |
| :- set_prolog_flag('double_quotes','chars'). | |
| main :- Term = (member(Z,A),append(A,B,C),dif(A,[true,false])),has_type(Term:Type,Types),writeln('Term with types to infer:'),writeln(Term),writeln('Types of variables in this term:'),writeln(Types). | |
| greater_than(A,B) :- | |
| A > B. | |
| matches_any_([],B) :- false. | |
| matches_any_([A|A1],B) :- | |
| subsumes_term(A,B),A=B;matches_any_(A1,B). | |
| matches_any(A,B) :- | |
| nonvar(A),matches_any_(A,B). | |
| has_type(Var:number,_) :- | |
| number(Var). | |
| has_type(Var:[list,_],_) :- | |
| Var == []. | |
| has_type([A|B]:[list,T],List) :- | |
| is_list(B), | |
| has_type(A:T,List), | |
| has_type(B:[list,T],List). | |
| has_type(Var:number,List) :- | |
| matches_any([sin(A1),cos(A1),tan(A1)],Var), | |
| has_type(A1:number,List). | |
| has_type(Var:bool,List) :- | |
| matches_any([not(A1)],Var), | |
| has_type(A1:bool,List). | |
| has_type(Var:bool,_) :- | |
| Var==true;Var==false. | |
| has_type(Var:bool,List) :- | |
| matches_any([member(A,B)],Var), | |
| has_type(B:[list,T],List),has_type(A:T,List). | |
| has_type(Var:bool,List) :- | |
| matches_any([append(A,B,C)],Var), | |
| has_type(A:T,List),has_type(B:T,List),has_type(C:T,List),T = [list,_]. | |
| has_type(Var:bool,List) :- | |
| matches_any([(A,B),(A;B),(A->B),forall(A,B)],Var), | |
| has_type([A,B]:[list,bool],List). | |
| has_type(Var:number,List) :- | |
| matches_any([(A+B),(A-B),(A1*B),(A/B),A**B],Var), | |
| has_type([A,B]:[list,number],List). | |
| has_type(Var:bool,List) :- | |
| matches_any([(A>B),(A<B),A>=B,A=<B],Var), | |
| has_type([A,B]:[list,number],List). | |
| has_type(Var:bool,List) :- | |
| matches_any([(A==B),(A=B),(A \= B),(A \== B),dif(A,B)],Var), | |
| has_type([A,B]:[list,_],List). | |
| has_type(Vars,List) :- | |
| var(List),List=[_|_],has_type(Vars,List). | |
| has_type(Var:Type,[Var1|Rest]) :- | |
| var(Var), | |
| (Var:Type == Var1;var(Var),var(Var1),(Var:Type) = Var1; | |
| nonvar(Var1),Var1=V1:T1,(V1==Var,Type=T1; | |
| (V1 \== Var),has_type(Var:Type,Rest))). |
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