I just release App::GUI::Harmonograph for your leisure and pleasure. In case your not not an English noble man form the 18th century who could afford an Harmonograph, even though modern DIY kits are quite affordable, it is a set of set of 3 independent pendula, which move a pen and and paper to create harmonious drawings, of sometimes extraordinary elegance and richness. I got the impulse and knowledge of the apparatus from this book and refer for more background details to this publication. However, the documentation (which is also displayed by the program itself) is much more of practical use, because the WxPerl version is greatly enhanced in possibilities, not in the least for dotted lines with variable density an additional rotation movement and flowing colors.
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on July 9, 2023, at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.
Task 1: Special Notes
You are given two strings, $source and $target.
Write a script to find out if using the characters (only once) from source, a target string can be created.
In Perl there is an expression
local
. It substitutes the specified value with undef until the end of the block. The values can be global hashes, arrays and scalars, as well as elements or slices of hashes and scalars.
The problem is that package hashes are not saved by local.
By package hashes I mean a hash with a colon at the end (%Package::) which stores the package symbols (GLOB).
I introduce the progress of the new class feature of Perl. If you are interested in the progress of the new class feature of Perl, please see the following topics.
A program being executed, self terminating on encountering an non-viable condition is a typical scenario in Perl programs. The death sentence can deliver information about the departed application to the user as justification and demand appropriate resolution for the subsequent reincarnation.
Now I know my code fails more often than it succeeds, and it is for this reason I am planning an alternative wake for the programmed parting of my future terminal applications. As a once-in-a-run-time event, death might be more elaborately delivered, something to be celebrated. The last words of a dying application softens the developers ensuing grief, while encouraging resuscitation with an appropriately delivered injection of code.
Imagine my code being transformed from:-
do_something_risky() or die "you evil monster $!";
into
get_away_with_it() or deathSentence($!)
producing something like this on the terminal:-
I know such distraction wastes time, there are probably many more error trapping and diagnostic tools available. These may be absorbed over time...I am not really an expert. But I am collecting a series of reasonably uncontroversial, hopefully humorous "epitaphs"...
You are given an array representing box coins, @box.
Write a script to collect the maximum coins until you took out all boxes. If we pick box[i] then we collect the coins $box[i-1] * $box[i] * $box[i+1]. If $box[i+1] or $box[i-1] is out of bound then treat it as 1 coin.
Example 1:
Input: @box = (3, 1, 5, 8)
Output: 167
Step 1: pick box [i=1] and collected coins 3 * 1 * 5 => 15. Boxes available (3, 5, 8).
Step 2: pick box [i=1] and collected coins 3 * 5 * 8 => 120. Boxes available (3, 8).
Step 3: pick box [i=0] and collected coins 1 * 3 * 8 => 24. Boxes available (8).
Step 4: pick box [i=0] and collected coins 1 * 8 * 1 => 8. No more box available.
Interestingly (to me, at least) they reported that the removal of the /o modifier made their case 2-3 times slower. This surprised me somewhat, as I had understood that modern Perls (for some value of "modern") had done things to minimize the performance difference between the presence and absence of /o.
They indeed have.
Ironically, it’s qr objects which don’t get that benefit. On the machine I’m typing on, the following benchmark…
O wad some Power the giftie gie us
To see oursels as ithers see us!
It wad frae mony a blunder free us,
An' foolish notion: ...
My previous blog post, Match Anything, Quickly, brought a number of responses which are worth reading in their own right. The one that triggered this post, though, was from Nerdvana and Devin of Cincinnati Perl Mongers, who pointed out an error in my benchmark script. I had left off the intended /smx from the qr/ ... / version of the test, which meant that the regular expression did not in fact match.
Three cheers for code reviews!
The Cincinnati Perl Mongers came up with a further case which combines my two:
Programming in Perl is choices all the way down. Perl is a multi-paradigm programming language which means that Perl can support the development of software using different programming paradigms, e.g. functional programming, object-oriented programming, and more.
Programming languages are culture, and culture follows philosophy. Philosophy is how every culture provides itself with justification for its decisions, values, beliefs, and worldview.
Perl's philosophy
Perl's philosophy is TIMTOWTDI, i.e. “there’s more than one way to do it”. You might even say that Perl takes the position of not taking a position, and this disposition applies to the topic of a standard library as well.
To be clear, what some will call Perl's standard library is little more than a grab bag of functions, pragmas, and packages shipped together with the core. This collection is a mix of functional and object-oriented styles and is intentionally lightweight.
It’s probably worth mentioning that the Raku team has also adopted this posture (and tradition).
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on July 2, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.
Task 1: Count Primes
You are given a positive integer, $n.
Write a script to find the total count of primes less than or equal to the given integer.
Example 1
Input: $n = 10
Output: 4
Since there are 4 primes (2,3,5,7) less than or equal to 10.
Following from my previous post, I am now actively encouraging everyone to switch licenses to MIT/ISC license or Apache 2.0.
My reasoning is that in the vast majority of cases the author and contributors want the software to be used by as many businesses and hobbyists as possible.
Previously I described how the burden of understanding and complying with licenses, including open source licenses, can be an unintended barrier to them using the software.
Perl modules tend to use "Perl 5" combination as the default license i.e. "Licensed under the same terms as Perl itself". And the "Perl 5" license is actually a dual licensing of the problematic Artistic 1.0 license and the dated GPL1.0 license which also has problems. Both are rarely used outside of Perl and in my view present a barrier to adoption.
Recall I described how permissive ("BSD") and copyleft ("GPL") licenses are functionally identical if no binary is distributed (websites) or for scripted languages that remain in source form.
Hello ,
When "use DateTime;" library is included in perl file ,getting the error as
"CPM0 frl-plugin:perlscript: ERROR: 'times' trapped by operation mask at /usr/lib64/perl5/B.pm line 183."
Could someone provide some inputs on the same.
Also to which tag does this opcode 'times' belong to ?
example: fork,wait, waitpid will belong to :subprocess
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 25, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.
Task 1: Matching Members
You are given a list of positive integers, @ints.
Write a script to find the total matching members after sorting the list increasing order.
Revision: that Cincinnati Perl Mongers found an error in the benchmark script used for this post. Match Anything Quickly - Revision 1 discusses their findings and links to a revised benchmark script. -- TRW 2022-09-02
Sometimes I want to filter a set of strings, but the details of the filter are not known beforehand. In particular, I may want a null filter, which simply accepts anything.
This looks like a job for a regular expression, but I can think of at least two implementations. One is to pass around regular expression objects. The second is to wrap a match (m//) in a subroutine reference, and pass that around. Given the use of regular expressions, there are a number of possibilities for a regular expression that matches any string.
I will get it wrong. I will start off by saying that, not just because I am married and this sentiment has been conjugally programmed in me for years, but because doing things "my way" will not suit everybody. We approach life, programming, drawing from different perspectives, different analogies, and one method however disagreeable to one person, may be perfectly logical to another. Even our own actions and analysis show conflicts. Take a cup of tea. I drink from the top of the cup, but measure from the bottom. Take character position in programming code...we measure lines from the top, then character on that line. But when we write, we write one line at a time, populating columns in a line before going to the next line.
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on June 18, 2023 at 23:59). This blog post offers some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.
Arithmetic Subsequence
You are given an array of integers, @ints.
Write a script to find the length of the longest Arithmetic Subsequence in the given array.
A subsequence is an array that can be derived from another array by deleting some or none elements without changing the order of the remaining elements.
A subsequence is arithmetic if ints[i + 1] - ints[i] are all the same value (for 0 <= i < ints.length - 1).
I have always understood that variables whose names begin with anything but an alphabetic or an underscore are reserved to Perl, and you mess with them at your peril. And this is the gist of the Porters' response to the post. Recent versions of perlvar say this explicitly, though earlier versions of that document restrict themselves to describing currently-implemented special variables.
For what it's worth, perl532delta appears not to mention this as a new diagnostic.
I wondered how much of this kind of thing was in CPAN, so I whipped up a Perl::Critic policy to try to find them: Variables::ProhibitNumericNamesWithLeadingZero. I then ran this against CPAN as it stood July 23 2022.
In the year 2000, the world was a different place. Y2K was still fresh in our memories, many of us had just partied like it was 1999 and Mark Fowler had given up eating chocolate.
