How to create a list in prolog. Querying a Prolog knowledge base.

How to create a list in prolog So the following is true: memberCheckSimple([H|T], H). It can easily be define by retrieving, the 3. The "list of lists" part comes from the fact that the OP wants to compute one list of results per line of the file; but what the question is really In Prolog, we can create a list from facts by defining predicates that represent the elements of the list and then using a predicate to combine them into a single list. Add accumulator for current index, succeed when heads are same You are already very close to the solution, so I only rephrase what you are beginning to sense already: First, you cannot modify a list in pure Prolog. Here are a few comments. rate(X,[_|T],N) :- rate(X,T,N). And there are some I'm trying to create a list in Prolog (SWI Prolog) and check which numbers are powers of 2 and second find how many times a specific number is in the list (in this example Prolog how to utilize list element as a variable in a predicate. This is not only a good I would solve it by comparing the first index of the first list and adding 2 to the index. I. See e. Whoa there, the first clause of choose/2 isn't what you want. 2 How to append list to a list in Prolog? 0 Prolog append to list. Ouput is List, which is a variable, hence changing is not possible. Hot Network Questions Permanent night on a portion of a planet When shouldn't I use possessive I'm new to prolog and I'm doing some exercises for practice. But I do not know how to check for indexes in prolog. the suffix elements of the first I'd like to know how to make a predicate that puts all results obtained from some query (so I get a result and press semicolon until I get False) in a list. In specific - I am trying to get through a list of items and copy it, item by item into I have code in PROLOG: vals(_,[],_). Although it's working, it can be tidied up a bit which will also help understand how Prolog works. Then make an Using the func library for SWI-Prolog, it is possible to write list comprehensions in a more concise way::- use_module(library(func)). The program will ask Input a number of elements: 6. Prolog - how to generate list of specific length? 1. We can prepend an item @repeat and anyway, I would also rather say must_be(list, X) for the first argument than use the maplist+append/2 solution that I originally suggested: although you do get I use SWI-Prolog and I want to make a list of several other lists. Prolog - Cartesian product calculator. Example: input is a list [a,b,c], I want to obtain the Note that if A is a list, then [A] is a different list, which consists of one element, namely, the list A. Many set operations on ordered sets are order N rather than order N**2. Prolog lists are denoted thus: The empty list is represented by the atom []. As you are a new user I won't down vote this question at this time, Prolog create list of lists. Thus we I'm try to make a list of the values n,n+1,2*n-1 for example if I have n=4 ==> [4,5,6,7] I have managed to write this code but it shows the list of first n elements. emacs. The list_to_set/2 Well checkNeq checks if none of the elements in the SubList is in our selected list. Thus, think in terms of describing when the relation I am having trouble how to do this on prolog. "choose([],_) :- !, fail. pair([],Q I am trying to create an included_list(X,Y) term that checks if X is a non-empty sublist of Y. – Limmen. So the first part says: concatenation([ ], Lista, Lista). Replacing in this Most prolog code will not define a list explicitly, like these examples, but rather handle lists of any length, with many possible elements. element of the matrix-list. You'd be What I need to do is to split one list [1,-2,3,-4], into two lists [1,3] and [-2,-4]. The first @Aspersum. Load 7 more related questions Show fewer related questions Sorted by: Reset To sum a list of numbers such as that produced by your definition of lists/1, most Prolog systems (e. now in the code above after compile buffer when I ask Prolog for a menu the menu appears with one choice and Prolog list - printing lists before and after element. Each fact The predicate notin describes an element that is not contained in a list and lt_list describes an element that is smaller than anything in the list by the standard term order. And you want a list of all lists' elements: maplist/3 does such mapping. % ?-pair([1,2],[a,b],Result). 1. In Prolog, within a clause, you can't modify a variable again once it's instantiated. In this case, there is nothing to do, so the body of the rule is empty as well. We'll present three examples of this in the forthcoming cards. Note however that the solution [3] for N=3 I'm programming in Prolog and I'm completely lost I keep mixing things up programming languages even if they're nothing alike I'm making a game called Meta-Forms as an Create a list in prolog. And I want to return a list that has a 1 I would like to solve a simple problem, but even through I tried many different approaches, I couldn't find a solution for it. Viewed 314 times 0 . For example?- find([20,1,2,3,4,5,6,7,8,10], L). [1,2,3,4] [[mary,joe],[bob,carol,ted,alice]] [] Another way to represent a list is to use the Element at head of list is larger than New element. That is not possible in prolog, you have to create a new variable. and what I did is. Some additional list manipulations are built-in. In standard Prolog, sort/2 can be used to create an ordered set. I find that it helps me to read Prolog from Right To Left (which I guess is natural from both our native tongues anyway, I guess). 4. The list is a data structure for grouping the entity to handle the application’s data. , GNU, SWI) implement sum_list/2 which takes a list of numbers as the What if we've reached the end of that list? Then we've arrived at the empty list, and appending an empty list with another list gives us that list as the result. But, if someone can figure out a solution As you write yourself, this is very unnecessary in Prolog. You could also consider a slower method, IMO useful Swi prolog has an emacs-like editor that you can bring up by typing. (a,[]) [a,b] is syntactic sugar for the term . To handle lists without knowing what's Your tree has, based on the question, two "families" of data: the constant void; and; a compound term with a tree/3 with as arguments the value and the left and right subtree. Prolog Lists from List Predicate. Actually doesn't matter if it's first or last. As an example, say I have the I want to access list permutation and pass it as argument to other functions. A difference list is a list expressed using a term with two lists. The list is a collection to This is not a discussion site. " numberofhello(N) :- my_list(L),counthowmany(hello,L,N). , memberchk/2, I am attempting to get my arms around some basic prolog but struggling a bit in the process. I'll let you work out the details and ask for help if it's still I was resolving some prolog exercises when I fond myself with some difficulties resolving the following one: Consider you have this fact base about object: object(obj1). I need to create a list of empty lists ex [ [], [] , [] , [] ] but Introduction to Prolog list. Ask Question Asked 9 years, 1 month ago. The trick with prolog is that. ** EDIT - The predicate for accessing a single list element is the most basic Prolog building block: member/2. How can I create a function in prolog that iterates through a list of lists and before passing to the next list goes through the one it´s pointing at? Ask Question Asked 1 year, 8 You thus can not "create" a list by first initializing it to [] and then later "altering" it, since altering is (or well should) not be possible. Before the next step, you have to get a no, it is just a question of interpretation. 1 and the target number are not included in the list. Prolog is not a functional language, so you can not type L+1 and expect it to be evaluated to You need special declarations to handle lists of multiple-type elements, because Visual Prolog requires that all elements in a list belong to the same domain. My code looks like the following: lists([],_,_). Then the prolog will sort into an Prolog reverse list is defined as the reversing of the given list, it means this operation is used to find reverse of a given list by using prolog programming language, prolog I am trying to count how many times a element appears in a list, so far I have came up with. create_list(_size,X):- _size>0, _last_size is _size-1, create_list(_last_size,Y), random(0,9,_random), X=[_random|Y]. I It takes the first element of your first list and plugs it into the resultant list, then recursively calls itself without the first element of the list meaning it will move onto the second It takes the first element of your first list and plugs it into the resultant list, then recursively calls itself without the first element of the list meaning it will move onto the second How to read an array "list" & print it in prolog ? I need to :- Prompt user to insert an array The user some how tells me that He's finished Then I print it . Hot Network You can play that out as follows. This predicate looks like this is implemented in C though. I'm working on creating a board used for the Bert Bos puzzle, and I'm trying to represent the board as a list of lists. Then the user will input 6 numbers , 4, 3, 6, 2, 9, 10. The name test is quite generic and a better name should be used. 6. I'm trying to use this: An example use of list construction is when we wish to create a new list out of two existing lists. Or in code, where we relax the "if and only if" equivalence to "if", which is good enough Expected behavior is for factors(A,16) to return the list [2,4,8]. takeout(X,[F|R],[F|S]) :- takeout(X,R,S), write(S). or: The goal is to avoid constantly entering long lists into the Prolog interpreter and instead store them in the . % Result= [{1,a},{1,b},{2,a},{2,b}]. Then the prolog will sort into an Prolog reverse list is defined as the reversing of the given list, it means this operation is used to find reverse of a given list by using prolog programming language, prolog is a logical and declarative programming I am trying to count how many times a element appears in a list, so far I have came up with. That is, it's a list of lists which contains one element. For example, in your case, it seems you already have a predicate like size/2 is a far simpler case and following the same process of base + inductive you should be able to create the rules for it. I have what you could call the filter ready, but I can't apply it. Prolog - How to make a list of lists I've very recently started looking into Prolog, and while I'm very unfamiliar with it still, so it seems "weird" compared to the other languages I've used before (C#, Java etc), it's Here is a general methodology for debugging and testing Prolog predicates: Start with the most general query! Think of it: In Prolog you do not need to make up some test data. There is a fair agreement on the semantics of most of these predicates, although error handling may We can use this construction technique to build lists during recursion. List Construction Example 1. vals([H|T],[(H,C)|L],K) :- vals([H|T],L,(K,C)). Please comment if you need further help. The 1 is already being handled in the first statement. This means that result list should be New element followed by head followed by rest of list. pl file. I have implement the following rule (that don't work well): I am really new in prolog programing and I can just ask simple questions. Prolog counting knowledge base . The prolog list is a function for collecting several values to operate on large-size data. Prolog To fix your code, the way you intended it, you just need to transform Head into [Head] in your last call to concat/3 in your last clause. Second, using predicate names prefix can easily clash with existing built-in and library predicates. If you want to get a useful answer, you might need to divulge more information about the task you have been given. A possible solution could be to create a list of N lists of size N, but now sure how to code this in Prolog. Even simpler: we just grab the head of the "front" list, unify it as the You may look at this link: Prolog program to merge two ordered lists This will not give you the output you need, but it is a start. Modified 9 years, 1 month ago. The list's I want to append are elements within a list. I check if element In Prolog, I'm struggling to understand how to bind a list of lists to a variable. 5. I am using SICStus Prolog (if that matters), and I If you want that SWI-Prolog will show the whole list by default you can add this line to your init file::- set_prolog_flag(answer_write_options,[max_depth(0)]). transfer java code into Prolog it seems you think in procedural or object-oriented code and want to use the knowledge as I am new to prolog. If you want to create a list of consecutive numbers from 1 to N you can use builtin predicates findall/3 and between/3 this way: do_list(N, L):- findall(Num, between(1, N, Num), L). '(H,T) in Prolog, but Prolog offers a You can implement the sorting algorithm yourself, writing predicates. I am having trouble how to do this on prolog. The clues to rethink this to use Tail Recursion Optimisation are valid, but if This library provides commonly accepted basic predicates for list manipulation in the Prolog community. For instance, the random library has a predicate that will Based on the way you are asking your questions, i. Let’s implement it using selection sort. I want to rotate lists to left in prolog like following: rotatelist([1,2,3,4],R) R=[2,3,4,1] I tried the following co You need to create a predicate that receives the item (list in this case) you want to append to another input list, and this would give you a new list with the which has all the items Prolog isn't like other languages in how it handles variables. ; We Note that empty lists are removed. Swi prolog comes with a lot of graphical The question's title is badly chosen. An example use of list In this post, I will show you how to create, manipulate, and query lists in Prolog using some built-in predicates and some examples. Obviously. The most common representation uses (-)/2 as the I want a have a matrix of size N x N in SWI-Prolog. List = [a, b, c, d, e] ; here are some examples of lists, and what heads and tails they result in: In this tutorial, we explain what lists are and how to declare them, and then give several examples that show how you might use list processing in your own applications. I want to compute the possible combinations of pairs in the list. This is the permutation code: takeout(X,[X|R],R). Instead, you should In Prolog, functions work by recursion rather than iteration. You can modify the init file easily Just to be clear on terminology, details(Age,Name,Dob,Zodiac) isn't a list. You thus Take an element X and create permutations Ys1 without it in the original list. This code receivers list and list of tuples, for example: vals([1],[(1,4),(1,2)],X). In order to use a difference list, you need to keep track of the "hole" in the list (in this case, its tail). However, entering the commands above results in the list not SWI-Prolog has the predicate between/3. Instead the output is formatted as a bunch of individually changed lists. A list would be, I'm trying to create a program in Prolog, but I'm still new to it and not sure what the best approach is to generating a grid-like structure in Prolog. In response to point 2. It is so important to get it also automated because Verbally, the fail forces Prolog to back up to the last choice point it made and try using the next solution. For example, I want to put the following three lists [a,b,c] [1,2] [d] into a larger one that looks like I have the suspicion that you could give a much better (more general) criterion, even now without any further improvement. Something similar could be achieved in a Prolog fashion by doing something like How would I do this in prolog? I have already got this to make a sublist, but now need to make sure the first and last element of the second list are not included in the first list. [H|T] is syntactic sugar In the number to list direction there are infinitely many lists for any given number and, as mentioned above, they are listed in a fair manner, that is, all possibilities of lists of Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about The problem is that eventually, you will make a call to increasing/3 where X <= N is not satisfied, and then that predicate will fail, and thus "unwind" the entire call stack. Can you help me modify i Yes^_^ ,it looks like: there are three methods, 1:get N by first method, 2:i will create list and set his domin, 3: use List that create by second method for parameter of third method compare the elements of one list with the elements of another list in prolog Hot Network Questions How to check (mathematically explain) mean and variance for simulated The first clause processes the base case, when the list [] is empty. Commented May 6, 2017 at 18:52. The problem was that you called your I am a newbie to prolog and I find it hard to think in a recursive manner. I'm having trouble understanding why the following Your problem is that you're trying to treat the dynamic store as a list (you say so yourself, but board/2 is a predicate, not a list) and it isn't really fit for that purpose. Let me show you what I want below as comment. Recursion in prolog is pretty much identical to recursion in any other language. . Your editing of the answer by CapelliC to ask new questions is very wrong. lists([X|Xs],Y,Z):- lists Skip to main content. For instance, with I need to remove only one occurrence in the list. Well, write/1 and nl/0 don't produce choice points because they only I'm new in Prolog and I try to understand some basic stuff. нет! First, names are just to important to be left aside. How would I implement shoppinglist, based on the Lists are frequently used to denote collections of elements in Prolog, and Prolog has special syntactic support for lists. The problem likely stems from the Both the solution posted @dasblinkenlight and the original code in the question can be made tail-recursive by using accumulators, which would allow running in constant space:. Let’s get started! In Prolog, lists are Prolog - Lists - In this chapter, we will discuss one of the important concepts in Prolog, The Lists. , I am trying to dynamically assign strings the user provides and Prolog: How to create a list of predicates? 0. Prolog: create a list of empty lists. Prolog, how should I construct a list of list to a single list? 3. 2. (b,[])). How to write the result in list instead of printing out in prolog. e a difference list is always a pair of two terms, one being a list with the "hole" and the other When describing lists in Prolog, it is often useful to first describe how a single element looks like. so you would call it like between(0,5,X) to get the results you showed above. nth0((Index, List), Result) :- And the second term in the predicate deals with the case of dequeueing when the "front" list is not empty. And in case you don't want the values change back in case of backtracking, you can make them I think you should start by looking at a Prolog tutorial and pay particular attention to list processing examples (there are some examples with source online). How can I use a functor name like Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about I am trying to move all new lists that I create into one super list of lists. ?- If I have a list in Prolog such as X = [1, 2, 3, 4], how do I add the element 5 to the end of the list to have X = [1, 2, 3, 4, 5]? The append function needs two lists, ie append(A,B,C) to get A and B Virtually every Prolog system has library(lists), but the set of provided predicates is diverse. a list [2,2,4] can serve as a representation of set {2,4}. Prolog - finding the product of a list. I already use this for checking if the elements exist on the Y list EDIT: Solved the problem a different way, by removing the odd indexed elements rather than trying to create a new list and copying the data over. Also, I would create a counter that I have created a random binary generator but it's "output" are written numbers, how i can make them a list? bin_gen(0). What you have is a good start and nearly functional. The Next, Prolog tries to unify Y with [], again trivially succeeding, but this time establishing the binding Y = [] which it reported to you. the problem of multiplicity never arises because that I want, given a list formed by A-B elements ([a-b,b-c,c-d]), check if some given element it's already in a list (which I will return), and if it's not, add any "A" or "B" element that I'm new in Prolog and I can't figure out how to obtain the result. Suppose I have two lists: list1[0,0,0,1,1,0,1,1], list2[1,0,1,0,0,0,1,1]. We'll illustrate this by defining a predicate called append that takes three arguments. So I'm trying to get the sum of the given numbers in a list. For list processing, this means (in general) you have to decide how to handle the empty list and how to handle an in short: How to find min value in a list? (thanks for the advise kaarel) long story: I have created a weighted graph in amzi prolog and given 2 nodes, I am able to retrieve a list of As an alternative to BLUEPIXY' answer, SWI-Prolog has a builtin predicate, max_list/2, that does the search for you. We also define two well Lists and Sequence in Prolog with Tutorial, Introduction, Starting of Prolog, Prolog Programs, Types of Prolog, Applications of Prolog, Backtracking in Prolog etc. One match needs to be removed. The primary mechanism of Prolog is In SWI-Prolog you can use: b_setval(name, value) and b_getval(name, value). This example is a relay race and the rules are As hinted in Carlo's answer, L+1 is a Prolog term with two arguments, L and 1, whose functor is +. The first thing to write is a min predicate which relates a list I am in the following situation: I have a list and I would to delete from it only the last element. Stack How about this: A list has the "list of list" quality if and only if all of its elements are lists. @lurker: au contraire. You know that if the element is at the head of the list, that it is an element of the list. Why? Because that looks [verbose mode ON] A list in Prolog is either the empty list [] or a head and a tail, which is technically represented by the "dot" functor, '. L = [20, 2, 4, 6] Normally in In Prolog, you establish bindings (or assert facts into the dynamic store, which is a tar pit for beginners). For example if I write The third list must contain the index of the positions in which the first two lists contain the same value. Prolog - how to print a list. The second clause processes One should note that to append an item to a prolog list requires traversing the entire list, prepending is a trivial operation, due to the structure of a prolog list. You cannot do exactly what you're asking for. insert(=, X, _, Xs, [X|Xs]). [a] is syntactic sugar for the term . If the list it empty you should produce no solutions instead of unifying Elt with the empty list. Querying a Prolog knowledge base. If we have to I'm currently working on a very short project on Prolog, and just got stuck trying to apply a "filter" I have created to a list. Lists The program can even be used to 'create' a list: ?- listsplit(List, a, [b,c,d,e]). (a,. It is a data structure that can be used in different cases for non-numeric programming. There are some noteworthy exceptions (like . Generally, what I am trying to do is to return a functor for a given list. The way to create a list in Let's look at your get_squared_pair/2 first. /* H If we're willing to depend further on SWI-Prolog there are some built-in libraries that can simplify this process even further. For instance, say I have the predicate makeList (which I don't know how to write), then I should be able to type: A list is just a term dressed in fancy clothing. You have I am currently attempting to write a Prolog program which will add a given character to the end of a list. Or use your own editor & then consult the file. Adding this element X as the first element of all these permutations we have the list XP of permutations starting The example given in the Question suggests that compositions (ordered partitions) of any positive integer N &leq; 10 are wanted. 0. And that's what that 2nd I have a problem like this: find all elements in a list such that all element(s) immediately besides it is/are odd numbers. Prolog: Build a list with repeated elements of other list. Check out my answer to the related question "How to count number of element occurrences in a list in Prolog"!In that answer I present the predicate list_counts/2, which And in such cases, there is nothing to "repeat" yet: We start from nothing, and ask Prolog what solutions there are in general. bin_gen(Y) :- random(0,2,S),write(S),Y1 is Y - Prolog's list notation is syntactic sugar on top of very simple prolog terms. So in this case you can simply revert the clause \+ member() to just member()in that Prolog create list of lists. I I am studying Prolog and I find it difficult to implement a predicate that takes a list and builds a balanced tree from it. how to print something inside a If you want to combine two ground lists with a possible overlap into a third one keeping in the result only one copy of the overlap elements (i. g. e. [] is a simple atom. After some tries, here is the correct answer, At least in SWI Prolog, for that to evaluate write Total is Head + Sum1 instead of using the = sign. there's no problem there. I have implemented these predicates that build an AVL You are right, coming from a procedural/imperative programming background is difficult. at the prompt. rate(X,[H|T],N):- X == H, N is N+1, rate(X,T,N). More about Prolog data structure Prolog List Notation In Prolog list elements are enclosed by brackets and separated by commas. every variable is local, and, once unified, variables cease to be variables. It's a relation consisting of a functor (details) and 4 arguments. I just can't think of how to To append lists efficiently, consider using difference lists. append(X, B, X) says, List X is create_list(0,X):- !, X=[]. This is what Using select/3 twice (or select/3 once and member/2 once) will allow you to achieve what you want here. zntv ubq iqx wrk lgcja xov snga wirf jokz mzha