Open-source News

LLVM's BOLT Flipped On By Default For Linux x86/AArch64 Test Releases  Phoronix

Microsoft has issued a big update to their in-house Linux distribution, CBL-Mariner, with a few new packages introduced as well as various updates to existing packages and other OS modifications...

Microsoft Issues Big CBL-Mariner 2.0 Linux Distribution Update  Phoronix

Star Labs new StarFighter sounds like a great Linux laptop  GamingOnLinux

How to Create Better Linux Terminal GIFs With VHS  MUO - MakeUseOf

How to iterate over tables in Lua Seth Kenlon Fri, 11/04/2022 - 03:00

In the Lua programming language, an array is called a table. A table is used in Lua to store data. If you're storing a lot of data in a structured way, it's useful to know your options for retrieving that data when you need it.

Programming and development Red Hat Developers Blog Programming cheat sheets Try for free: Red Hat Learning Subscription eBook: An introduction to programming with Bash Bash shell scripting cheat sheet eBook: Modernizing Enterprise Java An open source developer's guide to building applications Creating a table in Lua

To create a table in Lua, you instantiate the table with an arbitrary name:

mytable = {}

There are different ways you can structure your data in a table. You could fill it with values, essentially creating a list (called a list in some languages):

mytable = { 'zombie', 'apocalypse' }

Or you could create an associated array (called a map or dictionary in some languages). You can add arbitrary keys to the table using dot notation. You can also add a value to that key the same way you add a value to a variable:

myarray = {}
myarray.baz = 'happy'
myarray.qux = 'halloween'

You can add verification with the assert() function:

assert(myarray.baz == 'happy', 'unexpected value in myarray.baz')
assert(myarray.qux == 'halloween', 'unexpected value in myarray.qux')

You now have two tables: a list-style mytable and an associative array-style myarray.

Iterating over a table with pairs

Lua's pairs() function extracts key and value pairs from a table.

print('pairs of myarray:')

for k,v in pairs(myarray) do
  print(k,v)
end

Here's the output:

pairs of myarray:
baz     happy
qux     halloween

If there are no keys in a table, Lua uses an index. For instance, the mytable table contains the values zombie and apocalypse. It contains no keys, but Lua can improvise:

print('pairs of mytable:')

for k,v in pairs(mytable) do
  print(k,v)
end

Here's the output:

1   zombie
2   apocalypseIterating over a table with ipairs

To account for the fact that tables without keys are common, Lua also provides the ipairs function. This function extracts the index and the value:

print('ipairs of mytable:')

for i,v in ipairs(mytable) do
  print(i,v)
end

The output is, in this case, the same as the output of pairs:

1   zombie
2   apocalypse

However, watch what happens when you add a key and value pair to mytable:

mytable.surprise = 'this value has a key'

print('ipairs of mytable:')

for i,v in ipairs(mytable) do
  print(i,v)
end

Lua ignores the key and value because ipairs retrieves only indexed entries:

1   zombie
2   apocalypse

The key and value pair, however, have been stored in the table:

print('pairs of mytable:')

for k,v in ipairs(mytable) do
  print(k,v)
end

The output:

1          zombie
2          apocalypse
surprise   this value has a keyRetrieving arbitrary values

You don't have to iterate over a table to get data out of it. You can call arbitrary data by either index or key:

print('call by index:')
print(mytable[2])
print(mytable[1])
print(myarray[2])
print(myarray[1])

print('call by key:')
print(myarray['qux'])
print(myarray['baz'])
print(mytable['surprise'])

The output:

call by index:
apocalypse
zombie
nil
nil

call by key:
halloween
happy
this value has a keyData structures

Sometimes using a Lua table makes a lot more sense than trying to keep track of dozens of individual variables. Once you understand how to structure and retrieve data in a language, you're empowered to generate complex data in an organized and safe way.

Create structure that makes it easier to find stored data.

Image by:

Opensource.com

Programming What to read next This work is licensed under a Creative Commons Attribution-Share Alike 4.0 International License. Register or Login to post a comment.

Linux Foundation CKAD Dumps - Know The Value Of Real CKAD Exam Questions  NextPit International

The post Best RDP (Remote Desktop) Clients for Linux first appeared on Tecmint: Linux Howtos, Tutorials & Guides .

Brief: In this tutorial, we look at some of the best RDP clients for Linux. Sometimes, you might be required to remotely access your PC in order to carry out a few tasks. You

The post Best RDP (Remote Desktop) Clients for Linux first appeared on Tecmint: Linux Howtos, Tutorials & Guides.

<p><span><span><span><span><span><span>So far </span></span></span></span></span></span><a href="https://www.redhat.com/en/authors/luke-shannon"><span><span><span><span><span><span><span><span>in this series</span></span></span>&amp

It’s Not Just You: Disney+ Doesn’t Currently Work on Linux  OMG! Ubuntu!

AMD Announces Radeon RX 7900 XTX / RX 7900 XT Graphics Cards - Linux Driver Support Expectations  Phoronix

As was expected, AMD's Lisa Su just announced the Radeon RX 7000 series "RDNA3" graphics cards. AMD continues to back their graphics processors by fully open-source Linux driver support and Linux benchmarks will come on Phoronix for launch. Here are the initial details on the announced Radeon RX 7900 XT and Radeon RX 7900 XTX graphics cards.

How to Use FSearch to Quickly Find Files and Folders on Linux  MUO - MakeUseOf

Play one of the greatest co-op shooters free this weekend  GamingOnLinux

Nitrux 2.5: The latest update to a radical Linux  The Register

With CPU core counts continuing to rise, we've seen various optimization efforts in recent times to help with the boot speed of getting large servers online. One of the latest discoveries can trim down the boot speed by up to 30 seconds for some large servers and what appears to be a next-generation AMD EPYC "Genoa" platform...

CyRC Vulnerability Advisory: CVE-2022-43945 buffer overflow vulnerabilities in NFSD  Security Boulevard

Next week already marks ten years since Valve made public their Steam on Linux beta builds while today Google has advanced Steam on ChromeOS / Chromebooks to beta. Back in March Google formally announced Steam for Chrome OS and began with alpha support for select devices. Today that support has reached beta with new device support, new features, and other improvements...

Thanks to Microsoft you could soon run multiple nested Windows inside Linux  Neowin

Steam on Chromebook is now in Beta with AMD support  GamingOnLinux