Spoiler Alert: This weekly challenge deadline is due in a few days from now (on December 18, 2022 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 Integers
You are given a positive integer, $n > 0.
Write a script to print the count of all special integers between 1 and $n.
An integer is special when all of its digits are unique.
Example 1:
Input: $n = 15
Output: 14 as except 11 all other integers between 1 and 15 are spcial.
Example 2:
Input: $n = 35
Output: 32 as except 11, 22, 33 all others are special.
... computer language design is just like a stroll in the park. Jurassic Park, that is. -- Larry Wall
Perl's grammar is inherently ambiguous. That is, it is possible for a syntactically correct chunk of Perl to have more than one valid interpretation. Maybe this is because Larry Wall is a linguist? After all, natural languages are full of ambiguity.
The ambiguous warning is part of the group syntax; that is to say, use warning 'syntax'; enables ambiguous, as well as other warnings in that group. Of course, if appropriate you can just use warning 'ambiguous'; if more precision is justified. Both warnings go back to Perl 5.6, when the warnings pragma itself was introduced.
As has become habitual, I present a random selection of instances of this warning. Normal text is from perldiag. Italicized text is mine.
When starting implementing the compiler part of this. I noticed that the grammar does not actually really work, especially if you introduce new lines. If I parse a file with 3 instructions, we catch the \n sometime and the asm-comment token is too greedy.
Let's change the ws rule to only capture horizontal blank (space and tab) and introduce an eol token, this makes the grammar more clear on what we are working on also.
There have been a couple of developments in PDL since the last announcement on here I could find, from 2013. To hypersummarise: 64-bit indexing, native complex number support, automatic pthreading using all available CPU cores, faster installation thanks to parallel-building, memory-mapped data, repository hosted on GitHub, easy to use "with" Inline. Returning you to the announcement:
PDL 2.063_01 has just been released. Notable changes since 2.062:
Various API changes (see below)
Improvements to $MACRONAME() handling including that arguments can now contain (balanced) brackets
redodims no longer leaks memory
The PROJ.4 interface has been updated to use the PROJ v6+ interface, finally
A zeroes() regression from 2.057_01 where it ignored the type of an input PDL has been fixed
PDL::Compression is now thread-safe (thanks Derek for the report!)
An attempt has been made to fix the older-clang/LLVM compilation errors - if you have clang 12.0.0 or earlier and can try installing this version and report results here, that would be very helpful!
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on December 11, 2022 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: Digital Clock
You are given time in the format hh:mm with one missing digit.
Write a script to find the highest digit between 0-9 that makes it valid time.
Example 1
Input: $time = '?5:00'
Output: 1
Since 05:00 and 15:00 are valid time and no other digits can fit in the missing place.
Warnings category syntax contains a number of sub-categories representing possibly-problematic syntax. These include ambiguous syntax, problematic bareword usage, invalid printf conversions, and more. But there are also syntax diagnostics that do not fall under any of the sub-categories. These tend to be a miscellaneous group, and a normal-sized blog post can do no more than to give a sample.
What brought this to my attention was a noisy test in Template-Toolkit. under Perl 5.35.2 and up. The noisy code was untainting a variable using code like
$foo = each %{ { $foo => undef } } if ${^TAINT};
This makes use of the fact that hash keys are (so far) never tainted. The new warning was each on anonymous hash will always start from the beginning.
You may have seen Ovid's recent post
on his discussions with the Perl Steering Committee
about moving forward with implementing an initial subset
of the Corinna proposal in the Perl core.
One of the issues that came up during those discussions was the best way to provide private
methods in Corinna. The current Corinna proposal is that this would be done (like almost
everything else in Corinna) via an attribute:
method do_internal :private () {...}
Thereafter, the do_internal() method can only be called from within
the current class, and is never overridden by derived-class methods when
it is called within its original class.
In other words, the :private method effectively prepends the following
code to the start of the method:
croak "Can't call method 'do_internal'"
if caller ne __CLASS__;
I explain JavaScript supported web scraping using Perl and Selenium::Remote::Driver. Selenium::Remote::Driver is a Perl module for Selenium. Selenium provides the APIs for JavaScript supported web scraping.
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on December 4, 2022 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: Binary String
You are given an integer, $n > 0.
Write a script to find all possible binary numbers of size $n.
Continuing from our last post, I talked about how ANSI Game Engine is a colourful telnet server. We left off with needing to fork the engines telnet server.
Player 2 has joined the game!
Time to level up our telnet server and make it multi-player with some knify forky.
I've added in the strftime identifier from Perl's POSIX module to help with time stamping the output. The setsid identifier is for starting a new session and group ID for each forked process. A.K.A, the child process. :sys_wait_h is for returning without wait after the child process has exited, using the WNOHANG flag when calling waitpid(). This provides non-blocking wait for all pending zombie children.
In 2022, the German Perl/Raku Workshop will take place in Leipzig. We are very happy to announce that long time Perl supporter Geizhals Preisvergleich sponsor the workshop.
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on November, 27, 2022 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: Binary Flip
You are given a positive integer, $n.
Write a script to find the binary flip.
Example 1
Input: $n = 5
Output: 2
First find the binary equivalent of the given integer, 101.
Then flip the binary digits 0 -> 1 and 1 -> 0 and we get 010.
So Binary 010 => Decimal 2.
A casual remark about closures which I made in My Favorite Warnings: redefine touched off a long off-topic exchange with Aristotle that I thought ought to be promoted to a top-level blog entry. The big thing I learned was that any Perl subroutine can be a closure. The rest of this blog will try to make clear why I now believe this. The words are my own, as are any errors or misconceptions.
The second sentence of Wikipedia's definition of a closure says "Operationally, a closure is a record storing a function together with an environment." This makes it sound a lot like an object, and therefore of little additional interest in an O-O environment.
This blog post addresses checksum and signature verification vulnerabilities affecting CPAN, the cpan client, and the cpanm client, which were published in a security advisory on 23rd November 2021. If you're not aware of this topic, you might like to start by reading the advisory. This post gives a high-level description of the issues, what has been done to address them, what is still left to do, and what you should do. If you have any questions on this, you can add comments here, or email the PAUSE admins (modules at perl dot org).
Before we dig into the details, we'll first give an overview of how the relevant parts of the CPAN ecosystem work.
If you're not interested in the details, skip to the section "What do you need to do?"
TL;DR: make sure your CPAN client uses https and a trusted mirror – such as cpan.org
Spoiler Alert: This weekly challenge deadline is due in a few days from now (on November, 20, 2022 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: Twice Largest
You are given list of integers, @list.
Write a script to find out whether the largest item in the list is at least twice as large as each of the other items.
Who knows what evil lurks in the hearts of men? The Shadow knows!
OK, Perl does not literally have a warning about a 1930's pulp fiction and radio serial character. But Perl 5.28 introduced shadow as a new warning category for cases where a variable is redeclared in the same scope. Previously, such warnings were under misc.
To tickle this it is sufficient to
$ perl -Mstrict -Mwarnings -Mdiagnostics -e 'my $x; my $x;'
If your Perl is at least 5.28.0, you get the diagnostic
Why ? Because I can. More seriously I have a project where I need to inject new Snes code in a running game and I want to express directly this new code in my Raku component (A webserver service). I want to have special sub that returns me Snes bytecode but that contains Snes assembler.
I tried injecting a SLANG in Raku already. Like writing my $byte-code = SNES lda $42; sta $54; rtl; But it’s rather tricky and I will probably just have a additional Slang with its own grammar in a dedicated file.
