RabbitFarm

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

Part 1: Find Words

You are given a list of words and a character. Write a script to return the index of word in the list where you find the given character.

This can be done with a basic predicate with findall. Or we can use maplist! maplist is more fun in my opinion, so we’ll go with that.

First off a small utility predicate to see if a word contains a given letter.

You can see that we are sending that previous predicate a pair. The first element in that pair is an index. Let’s build a word index, mainly for the sake of avoiding the use of between and findall. Those builtin predicates are fine, but aesthetically to me it seems nicer to not use them if we absolutely don’t have to.

Now we’ll use maplist to find the words.

The rest of the code just wraps this predicate into a file.

Sample Run

$ gprolog --consult-file prolog/ch-1.p 
| ?- find_words([the, weekly, challenge], e, Indices). 
 
Indices = [1,2,3] ? 
 
yes 
| ?- find_words([perl, raku, python], p, Indices). 
 
Indices = [1,3] ? 
 
yes 
| ?- find_words([abc, def, bbb, bcd], b, Indices). 
 
Indices = [1,3,4] ? 
 
yes 
| ?-
    

Part 2: Find Third

You are given a sentence and two words. Write a script to return all words in the given sentence that appear in sequence to the given two words.

In the first part I mentioned the between and findall predicates. Here we will use them to find successive words.

Finally, let’s assemble our completed code into a single file.

Sample Run

$ gprolog --consult-file prolog/ch-2.p 
| ?- find_third([’Perl’, is, a, my, favourite, language, but, ’Python’, is, my, favourite, too], my, favourite, Thirds). 
 
Thirds = [language,too] 
 
yes 
| ?- find_third([’Barbie’, is, a, beautiful, doll, also, also, a, beautiful, princess], a, beautiful, Thirds). 
 
Thirds = [doll,princess] 
 
yes 
| ?- find_third([we, will, we, will, rock, you, rock, you], we, will, Thirds). 
 
Thirds = [we,rock] 
 
yes 
| ?-
    

References

The Weekly Challenge 315
Generated Code

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

Part 1: Find Words

You are given a list of words and a character. Write a script to return the index of word in the list where you find the given character.

This can be done in essentially one line. Rather than write a true Perl one-liner for the command line though, we’ll package this into a single subroutine.

Here’s our one subroutine.

Putting it all together...

The rest of the code just runs some simple tests.

Sample Run

$ perl perl/ch-1.pl 
(0, 1, 2) 
(0, 2) 
(0, 2, 3)
    

Part 2: Find Third

You are given a sentence and two words. Write a script to return all words in the given sentence that appear in sequence to the given two words.

Similar to the first part this will be a single short subroutine. We’re just going to loop over the words and match as we go. There are two small things to note here: we strip out any punctuation from our sentence and the empty string q// is considered by Perl to be a false value. The latter is only important in that is how we initialize $next.

The rest of the code drives some tests.

Sample Run

$ perl perl/ch-2.pl 
(language, too) 
(doll, princess) 
(we, rock)
    

References

The Weekly Challenge 315
Generated Code