The fringe of a binary tree is the sequence composed by its leaves, from left to right. The same-fringe problem [Hewitt & Patterson, 1970] consists of determining whether two binary trees have ...

I am trying to run a simple gprolog to run on my Linux machine, GNU Prolog was installed from the Ubuntu Software Center. From the GNU Prolog Intro I got the following example, stored in HelloWorl...

I want to use a Python script as a frontend to a Prolog program that uses the SWI-PL engine. So, the components of the setup are: Python (2.7 or higher) SWI-PL: website here I've been looking ...

Do they exist? How are they implemented? The coroutining predicates of SWI-Prolog (freeze, when, dif etc.) have the functionality of guards. How do they fit in the preferred Prolog programming sty...

I was just introduced to Prolog and am trying to write a predicate that finds the Max value of a list of integers. I need to write one that compares from the beginning and the other that compares f...

As a simple exercise, I wrote my own permutation. This stack overflows: without(_, [], []). without(A, [A|T], T). without(A, [H|T], [H|G]) :- without(A, T, G). my_permutation([], []). my_permutati...

I've written a predicate, shuffle/3, which generates "shuffles" of two lists. When the second and third argument are instantiated, the first argument becomes a list which has all the elements of bo...

For example: isin([1,2,3], [1,0,1,2,3,0]) will yield true because 123 is inside of 101230 I wrote the following code: isin([AH|AT],[AH|AT]). isin([AH|AT],[BH|BT]):- AH = BH, isin(AT,BT), isin([AH...

I'm trying to learn the basics of Prolog and keep running into a existence_error with the following code. comes_after(m1, m2). comes_after(m2, m3). comes_after(m3, m4). comes_after(m4, m5). comes_...

I was testing my new version of SWI prolog and keep coming across the error :singleton variable. Example: member(X,[X|T]). member(X,[X|T]) :- member(X,T). finds the member of a list such as : ...

I'd appreciate it if someone could elaborate on the difference between the is keyword and the = operator in prolog. I saw this discussion in == and =, but it excludes is. The documentation talks ab...

What is the best way to convert binary bits (it might be a list of 0/1, for example) into numbers in a reversible way. I've written a native predicate in swi, but is there better solution ? Best re...

I am beginner in Prolog programming. I wrote this program to calculate the length of a list. Why is below program wrong? length(0, []). length(L+l, H|T) :- length(L, T). I wrote below program an...

All lists with one single element is easy to define using the Prolog prologue: ?- maplist(=(_),L). L = [] ; L = [_A] ; L = [_A,_A] ; L = [_A,_A,_A] ; ... . So this element is repeated over and ov...

I wrote the following program based on the logic that a prime number is only divisible by 1 and itself. So I just go through the process of dividing it to all numbers that are greater than one and ...

My professor gave this as an example of Prolog. It is a program that solves the Tower of Hanoi puzzle, where you have to move a stack of disks to another peg by moving one disk after the other, wit...

I'm trying to write a rule which decides whether an item X occurs exactly one in a list L. unique(X, [X|T]):- !, \+ member(X, T). unique(X, [_|T]):- unique(X, T). The rule works for determining ...

I am currently trying to learn some basic prolog. As I learn I want to stay away from if else statements to really understand the language. I am having trouble doing this though. I have a simple fu...

I have finished a homework assignment for my programming class. I was supposed to create a Prolog program that reverses a list. I, however, am having trouble understanding why exactly it works. %...

Can anyone explain the concept of free variables in Prolog. Is it similar to anonymous variables ? Or is there a difference. Also could be great if an example is given to explain.

I've been given the question: Define a predicate ordered/1, which checks if a list of integers is correctly in ascending order. For example, the goal ordered([1,3,7,11]) should succeed, as shoul...

I came across this natural number evaluation of logical numbers in a tutorial and it's been giving me some headache: natural_number(0). natural_number(s(N)) :- natural_number(N). The rule roughl...

Being a beginner to prolog, I am trying to remove all duplicates from a list. I do get a satisfying answer but this should be the only answer. Instead, prolog keeps on providing other answers. I tr...

Lets assume there is pure_2 Prolog with dif/2 and pure_1 Prolog without dif/2. Can we realize Peano apartness for values, i.e. Peano numbers, without using dif/2? Thus lets assume we have Peano apa...

So as the title says - how do you convert a string into an integer? the idea is something like this: convert(String,Integer). examples: convert('1',1). convert('33',33). I'm using swi prolog