RabbitFarm

The examples used here are from the weekly challenge problem statement and demonstrate the working solution.

Part 1: Missing Integers

You are given an array of n integers. Write a script to find all the missing integers in the range 1..n in the given array.

Our solution is short and will be contained in a single file that has the following structure.

This problem is straightforward to solve using member/2.

Sample Run

$ gprolog --consult-file prolog/ch-1.p 
| ?- missing_integers([1, 2, 1, 3, 2, 5], Missing). 
 
Missing = [4,6] 
 
yes 
| ?- missing_integers([1, 1, 1], Missing). 
 
Missing = [2,3] 
 
yes 
| ?- missing_integers([2, 2, 1], Missing). 
 
Missing = [3] 
 
yes 
| ?-
    

Part 2: MAD

You are given an array of distinct integers. Write a script to find all pairs of elements with minimum absolute difference (MAD) of any two elements.

The code required is fairly small, we’ll just need a single predicate and use GNU Prolog’s clp(fd) solver.

This is a good use of GNU Prolog’s clp(fd) solver. We set up the finite domain variables I and J to take values from the given list. We then find the minimum value of the differences and return all pairs having satisfied that constraint.

Sample Run

$ gprolog --consult-file prolog/ch-2.p 
| ?- mad([4, 1, 2, 3], Pairs). 
 
Pairs = [[1,2],[2,3],[3,4]] 
 
yes 
| ?- mad([1, 3, 7, 11, 15], Pairs). 
 
Pairs = [[1,3]] 
 
yes 
| ?- mad([1, 5, 3, 8], Pairs). 
 
Pairs = [[1,3],[3,5]] 
 
yes 
| ?-
    

References

The Weekly Challenge 327
Generated Code