% Predicate to start the measurement process
weight :- measure(0, 0, 0, 0).

% Predicate to handle the input and measurement process
measure(S_sum, S_num, O_sum, O_num) :-
    write('Enter weight (0 to stop): '), 
    read(X),
    ( X =:= 0 ->
        ( S_num =:= 0 -> AvgS = 0 ; AvgS is S_sum / S_num ),
        ( O_num =:= 0 -> AvgO = 0 ; AvgO is O_sum / O_num ),
        nl,
        write('The average strawberry weight: '), write(AvgS), nl,
        write('The average orange weight: '), write(AvgO), nl
    ; 
        accumulate(X, S_sum, S_num, O_sum, O_num)
    ).

% Predicate to accumulate weights and numbers of strawberries and oranges
accumulate(X, S_sum, S_num, O_sum, O_num) :-
    ( X >= 15, X =< 25 ->
        add(X, S_sum, S_num, NS_sum, NS_num),
        measure(NS_sum, NS_num, O_sum, O_num)
    ; X >= 125, X =< 200 ->
        add(X, O_sum, O_num, NO_sum, NO_num),
        measure(S_sum, S_num, NO_sum, NO_num)
    ; 
        write('Invalid weight. Please enter a valid weight for strawberry (15-25g) or orange (125-200g).'), nl,
        measure(S_sum, S_num, O_sum, O_num)
    ).

% Predicate to update the weights and counts
add(X, Sum, Num, NSum, NNum) :-
    NSum is Sum + X,
    NNum is Num + 1.
 

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About Prolog

Prolog (Programming in Logic) is a logic programming language associated with artificial intelligence and computational linguistics. It works through facts, rules, and queries, using a form of symbolic reasoning known as backward chaining. Prolog is declarative, meaning you describe what you want instead of how to compute it.

Sample Code

The following is a simple Prolog program that prints a greeting:

:- initialization(main).

main :-
    write('Hello, World!').

Syntax Basics

Facts

Facts represent basic assertions about the world.

likes(alice, pizza).
likes(bob, pasta).

Rules

Rules define logical relationships using facts.

friends(X, Y) :- likes(X, Z), likes(Y, Z).

Queries

Queries are used to find information based on facts and rules.

?- likes(alice, What).

Operators

OperatorDescription
:-Rule definition
,Logical AND
;Logical OR
=Unification

Lists

member(X, [X|_]).
member(X, [_|T]) :- member(X, T).

Recursion

Prolog heavily relies on recursion.

factorial(0, 1).
factorial(N, F) :-
  N > 0,
  N1 is N - 1,
  factorial(N1, F1),
  F is N * F1.

This guide provides a quick reference to Prolog programming syntax and features. Start writing Prolog code using OneCompiler’s Prolog online compiler today!