Episode: 2723
Title: HPR2723: Using Elm in context of 4X game client
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2723/hpr2723.mp3
Transcribed: 2025-10-19 15:40:34

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This is HPR Episode 2007-123 entitled,
using L-min context on Forex Game Client.
It is hosted by Tuku Toroto and is about 45 minutes long
and Karima Clean Flag.
The summary is Tuku Toroto's new decision-on-structuring L-application.
This episode of HPR is brought to you by an honesthost.com.
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Hello listeners, I'm Tuku and you're listening to the Hacker Pocket Radio.
The trick of today is riding L-client for the Forex Game that I'm working on.
Initially when I started working on the game,
I had an idea of riding it mostly with the HTML-client set that is
and only had a little bit of scripting here and there.
But as the work-progressor soon realized that it wouldn't work very well.
And there was some things that I perceived that might cause performance problems.
For example, if you are in the old way that I wrote when you opened a display or the page
that was used to design the spaceships, it always called to the...
It first loaded the L-program and then the L-program called to the server to load some data
that was needed for the seed construction or seed designing.
And if the user later on came back to that site, that back to that page, it did that again.
But that led me into thinking that maybe I should ride the whole client in an L-m
innovative. It loads the code only once and as the user navigates around the program,
it doesn't have to load the code over and over and over again.
And it also could cache some data that difficult doesn't change.
It wouldn't have to retrieve it from the server site.
For example, the technology, technology 3 that tells what the player has researched
and what they are able to build doesn't change that often.
So it wouldn't have to download that from the server all the time.
So all this led me into scrapping pretty much everything I wrote with the method
using Hamlet template and look into writing the client site with the L.
So as I said, back end of the server site is in the method.
It's called Haskell's framework for web platforms and the client site is written in the L.
So they need to communicate and for that I choose pretty standard rest interface,
rest place interface. So there's plenty of JSON data flowing to back and forth.
The back end and front end are printed in the languages that are static typing,
which made it all at least in this current project, I really like it, like it.
The transfer of data in between is of course in strings.
So you need to have a you need to pay or I need to pay attention how the how those strings
handled so that the data sent from the server does not change to something completely different
on the client site. But luckily the LM and Jesuit has a pretty cool good tools for this.
So my goal for this was to keep things as easy as possible, keep them type safe
and extensible because I don't have that clear idea of what I will be.
Writing in a couple of months for example.
And then this of course the things like user authentication,
authorization that I wanted to print to the client site to work some of you have to be able to
tell the difference between regular player and administrator because administrators have their own
set of views on the client site that they can use to examine the state of the system and
do maintenance and such things.
So there are typical architecture for the LM has four major parts, these are the model,
U, messages and update function. Model is a single type that catches the state of the program,
view is a function that when given a model will render HTML and that HTML may contain things that
produce events for example on click, handler on some link or button and those
are used to create messages or are instructed, the instruct LM that when you click this thing
you should create this kind of message. And the message is a single type again that catches all
all the interactions that the programs can have. For example, you should click in on some button
or program receiving a update from the server or program sending update to the server.
And the final final part is the update function that when given our
model current state of the program and a message will produce a new model and a possibly new message
to. So because of this I didn't have to really think how what the overall architecture of the
program that was already given to me but I had to figure out how to make this thing a sort of
extensible. There are multiple pages for example one page to view all the star systems that the
player has found and on nodes of another page to to look into details of one of those far
systems and then get another page to look into details of a planet and to the two things that
you usually do in a 4x game on planets constructing things, changing policies, things like that.
And I decided to split this thing into pages like there's a one function to render
each of these pages. Well I mean one function to render one page and then another function to render
another page and one function the page to handle the messages that it made create and then one
function to initialize the model when the page page is open. I put in our links into the
follow nodes into these examples of these functions and then there's a one function to
yeah the one function to initialize the model when the page is open. This is basically the two
when when user opens for example a planet view for for first time for a certain planet and
the client doesn't yet have a data that is needed for the explain that information. This
function will create a bunch of requests to the server that by the way I need the population
information for the earth and I need all the buildings allocated on the earth and I need
things that are being constructed on the earth and those are sent to the server and when the
response comes back that here's the data we store them into the model. There's a
for the for example for the buildings there's a dictionary for that is
the key to buy the planet ID actually it's key to buy the integrals because you cannot
exactly you cannot put self-defined pipes into the key to the dictionary you have to
cast cast them to integrals or strings for example there's only very few data pipes that you
can use as a key in the dictionary but in any case those are stored in the dictionary
and you can find them if you if you know the ID of the planet you can find
buildings that are being constructed on it and the view function that renders the planet
we look into that dictionary find that check if the if there's a buildings present present it will
render them name and level and damage I think info information when it was last observed
and if the information is in present it will just leave that part of the UMD
a property should put out some sort of indicator that will tell the user that the data is in present
and as soon as the update comes from the server it will it will change that part of the UI it will
Elm does it in a way that as whenever a model changes it will change the respective parts of the
UI on the on the on the on the browser these are called reactive programming and Elm is
even functional reactive programming really it's really nice I am very I'm very happy for
work with Elm because you can always at least I have the feeling that you can pretty much always
indicate things like for example if I have something that may or may not be present then the
data that the type of that is maybe that thing X maybe buildings if the building system type of
that tells me what kind of buildings are on the planet and then on the when I'm rendering on
the screen there's the Elm made sure that I don't just really really start rendering them it
forces me to check that hey this is this thing might or might might not be present the compiler will
tell me that you did not do that you have to do that it doesn't it doesn't type check so
on the rendering part I have to account both cases the information is present or information is
not present and that's that's that's captured on the type level in the model it actually it
really says that this might or might not be here and as soon as I soon as the thing changes the
UI changes okay so the model is split into couple parts you know in my system there's the
general path that holds all the common data like planets that have been the information on
the planets that have been retrieved from the service parts, how much resources the player has
what time is it in the game things like that that that can be used pretty much everywhere and then
there's a single type for each of the pages for example for the planets the I'm for the view that
is used to render or the page that is so shows the planet information there's a type called
planet r r has also copied the naming convention from the yes or
and that pipe holds the data that is needed for specifically for that page like if there's
a info panel that player can open or close or if they're the search fields that they can do
to use. That kind of information is used in that model. I mean, so in that, that is
a particular model pattern. Those two together are actually the latter one is part of the
first one. The view function that is used to render this planet information has, that
that function has all the information it needs to put rendering. Each page has their own.
I guess one could call it view model. I couldn't think that of the name, that holds that data
that is specific to that particular view. And this is the one that is inutilized by
e-function when a page is open first time. Okay, the message is there's a type that has
inventively named as a MSG, so opened of as a message that holds all the messages that the
program needs to react or send access to react to. And again, it has a separate
message for each of those different views. For planet, there's a planet message is for the
stars and these stars and messages. And that message contains usually the stuff that
only that page needs, needs users click the open this info panel that sends a specific
planet message. And then there's an app message that is used to deal with
responses for queries to the server. If my system has queried, has asked the server
to send information about the population on the planet, it will arrive back as an app message
population received and then the population received contains all the relevant information.
And this is a 100-part update function in the element. All the messages are
handled by the single update function. They come to the single single function that is in
charge of taking care of everything. And if you have a big program, it can get really,
really big. And that's not fun. So again, I split this into the smaller parts.
It's, I eat, subtab message, have their own handler. So when the, there's still one
update function that is in charge of dealing with the messages, but that can delegate the
handling to the other other other functions, depending on the type of the message that
actually arrived. I think that's all about messages. So where do these messages
are sent to this or rather way to this queries request sent to the LMSA type
URL or that is, that is, that is, that's it for the address to send data. And all the
end functions that deal with the networking use, use that one. I didn't want to use
that because that would mean that I would have to write the strings quite many
places. And I have, I have noticed that I tend to do typos in
those and that will lead into hard to debug problems because, because that will lead
into the incorrect behavior that is noticed only when the program is running. I rather
have the typos code in advance when you are, when you are compiling the program. One way
would, would be to define constants for this, but I thought that again,
borrowing something from the result, I made our own type called end point. And this
end point is used to capture, it has, it has all the end points or addresses that
you can call on the server side. For example, and that type even captures the
parameters that you need to send to the, you need to give to that type. For example,
if I wanted to request information about population on the planet, that type,
that constructor I would call is an API population, inventively named and that
takes a single parameter of the planet ID. So whenever I want to call to the
server and I want the API population, I can give this specific constructor data
constructor and the compiler will make sure that I have typed it correctly and I have
given it to a correct amount of parameters and those parameters of correct
byte. But of, and then on the behind the scenes, I have a function that will
turn this, because the, Elm of course does not understand these pipes. I had to,
first of all, I had to define my own versions of, of get, post, put and delete,
that not to the rest behavior. And these take these end points as one of the
parameters and then they understand how to get from the end point into the correct
URL byte. So mapping is in one place. And they also, that, for example, get
has information of what kind of event will be, what kind of message will be
created and what kind of decode or JSON files will be used to process this
data. So when the response comes back from the server into the update function
of ours, it, it has already been passed the JSON data has been mapped into
the Elm object. So it's very nice, it's pleasant to use. You don't have to,
there's a one place where you have to worry about transform taking JSON data
apart and constructing a Elm object and that places somewhere behind the scenes
that you don't have to worry about when you are doing these calls.
Same, same system is done with the pages instead of end point, this type is called
root. The idea is the same though, the root captures the different pages and
parameters that you are required to give when you want to move to that page.
For example, if you go to the home page, it's just a home or you don't need to
give any parameters to that. But if you are, you, if you want to send
user to a specific page about specific planet, it takes two parameters.
Planet R takes two parameters, star system ID and planet ID. And based on those
two parameters, there's a root to string function that understands that
planet R actually maps into the string that is slash star system,
slash and then star system ID, slash planet ID.
So again, the Elm, of course, the HTML function of the Elm don't understand
a path of roots. So I actually define my own version of HRED that works
identically to the Elm's HRED, but instead of taking a URL, it takes
my root parameter and then behind of the, when it's rendering the stuff on the
screen, it will actually use the correct Elm's HRED to output the data to
output the HTML that the browser understands. So this is a little bit of
good. And there's the whole Elm HTML library that is really good and
couple of little additions that are specific to the system data.
And here are the, since 0.19 version of the Elm, the Elm program can be made
aware of on what URL, URL is it is being run. So this allowed me to
wrote the system in a way that the server, the ESRD, will serve the same
Elm program from multiple locations. For example, if you go into the
homepage, it will serve the same Elm program as if you went to the, for
example, planet page or star system page or page about messages.
The all will serve the exact same Elm program. And the Elm program itself is
aware of URL where it was started, which allows it to, in the start
app, to move to that correct view, it will render. For the user, it will
look like they are, they are starting from different, different pages
within the program, as they actually are starting from the, from the different
pages within the program, but it's still the same Elm program in every, in
each and every of these cases. I made this because it allowed me to, for
example, this allows players to keep links to other players, if they, if they
have opened a specific, a planet, for example, they can set copy
the URL, mail that URL to another player and say that, hey, have a look at
this planet. And if that another player has sufficient information, they have,
they have observed that planet at some, at some point, opening, opening
that a URL will give them the correct, correct view, they can see the same
plant. And if they are, members of the same faction, they are getting the exact same
information even, because I, I, I had a feeling that it's important to, even,
even when the program, even when the client site is a single program, it is
important to give the user's ability to send links to another user
and have those links work in the way that they would work in a normal,
normal that, not, not, not in a case, not in a, because in some cases, they
are those single page applications where you cannot link into a sub-view.
And I don't like those. I think that, I think that the ability to link to
a specific point in a system is a very crucial integral part of the
web. Okay. Yeah. And now I lost my door. Okay. There's a part of this,
that was required for this is the, the, we have the function root
to string that when given a root will give you the correct
string that you can use in the URLs part to facilitate the mapping from the
another, another direction we have, we had to create a mapping that tries when
given a any kind of string as a URL will try to figure out what root
that this would be and part of that mapping for this is defined in the
function root that I have the definition of that in the show notes,
that only, that basically maps that if there's a, for example, if there's a
string profile, nothing else, it will map to the profile page within the
program, if there's a string star system slash star system ID slash
planet ID, it will not do the planet hard resource or root, sorry,
root. And then the top root home is used when passing fails.
So whenever you say, for example, if you use types that you have a
hello world, it will take them to the home root. And what else?
Predecramps, yeah, there's a part of the, the really, this one is actually
pretty proud of, I lifted the basic idea from the yesterday again, but
in top of the top of the page, there's a Predecramps, this is just a
hierarchical navigational age, it displays names of the pages that are
earlier and not early on the history, but sort of an above of this
specific page that users currently, when they are the very beginning
it shows just a home as a text, but if they click to the
better star systems, the Predecramps will read home slash star
systems. And now home is suddenly a link that you can click and get
back to the whole page. And on the star system page users have a
little list of star systems that they are aware of, all these
all these data that the client is showing is based on the, on the
reports that have been generated during the gameplay. I talked about
those earlier. And those, those, those reports are just telling
the user that this is how you observe the, how you observe the
world, this is the information you have, and the client is dealing
only on those reports, the client never ever sees the actual data about
what's the real state of the world. But I got lost, so when they
click a, for example, a solve system, now the Predecramps will
read home slash star systems slash solve, not star system, not
general name, but solve because that's the current system they are
viewing. And home and star system text are links to those
respective pages. And now the user are showing the details of the
solve system. They are a list of the planets that they are aware of
if they click the Earth, they are taken to the page that shows
the details of the Earth. And now the Predecramps will read home
star system, so home slash star system slash solve slash Earth.
And all about the Earth are links to the door to the rest of the
pages. This, the idea behind here is that the users are, they are
aware of where they have navigated, they have some sort of
contextual information of the location in the system, and they
are also given a tool to quickly jump back to somewhere. They can
use browser type button. Elm program will detect that now
they have requested moving to a different URL, and we will
serve the correct page, meeting the Elm program. You don't
actually exit the Elm program when you hit back or forward in
the browser. Until you go all the way to the back and you go
back from where you started from the Elm program, then you
of course are, the new, of course, leave the Elm program.
How, how, how game client and pretend to, was it
proved the start page of your browser, for example.
So the Predecramps are offered another way you don't have
to use the back button that you can directly, even if you are
viewing the third you can directly jump to the home page of
the game client. I'm just clicking that home link.
And these, these, these are defined. Well, there's a little
bit of functions that are not interesting, but the Predecramps,
I'm calling Predecramps past the whole thing, is made
in a, there's a function, Predecramps part that takes the
model and produces HTML, that's the whole whole thing.
And that also wraps it in a, some diffs and filings and
what not. The actual work, work is done in a function called
Predecramps, that takes the model, because you need to know
where you are, you need to, and then there's the
Boolean Slack, which tells you if you are on the first node
or in some other node, then it gives you the current
truth that you want to construct the Predecramps from and
it will produce you a list of HTML.
And this, this will call itself recursive,
recursively. The first, first one is called with the
flat being. Actually, I don't remember, I have to admit,
I don't have code, I have only the definition here.
I think it was called with the Boolean tree true,
meaning that this is the first element. And after that,
the recursive code will turn that Boolean to false,
but I'm not sure that which, of course, means that I should
get rid of the Boolean Slack and have a real pipe that
is, for example, the Predecramps placement that can
have two values, first and some other.
Because then it would be visible on the pipe definition that
what this Boolean Slack is actually used for.
It would have a sensible name and it would have, well,
it wouldn't have any more values or any less values than the
Boolean, but it would have a sensible name and it
could have a pipe and it would mean that you don't accidentally
stop something incorrect there. Or even at least it would make it
harder to put something incorrect there.
And that thing is calling third function called
decrement that takes the model root and produces a
couple of string and maybe root. The string here that
it produces is an actual text that is being shown.
For example, in case of the home page, it just reads home.
In case of the file system, it's reads star systems.
In case of the Earth, the planet Earth, it will read Earth.
And for that reason, the function needs the model because
the model holds the, all the data that has been
retrieved from the server, it has the dictionary that
has the, that has the planet information and that
dictionary is keyed by the planet ID that
integrally, because you still can't put the
planet ID as a key of the dictionary.
And based on that information, this segment
who understands that now we are on a, because
root is of course the planet A that has two parameters,
star system ID and planet ID. Based on that
information, that and the model that has
given the segment can read from that dictionary that
is in the model. The information of the planet
being currently shown and get the name of that planet
and put that written that, by the way, this is
not just any planet is, planet Earth.
And the second parameter on the
sample that is written is the neighbor root and
that is used to indicate the parent of the
this segment. In the case of the home, it's
nothing because there's no parent, but in the
case of the, for example, if we are navigating
to the, or have navigated to the view about
Earth, the parent will be star system A with
a correct star system ID. And this will
trigger the recursion in the
breadcrumb function, because it notices
that, okay, this has a parent, so it will
go to the, but it will call the segment
again. And in the root, it will give that
star system as a parameter that will
produce a double with a string as a
soil and just star systems A as a
parameter. And that, that will trigger
the recursion again and from the
decursion you are getting a home
actually, yeah, home and nothing,
because home doesn't have a parent anymore.
So the, when, wherever you are,
wherever the user is within the system,
the breadcrumb path, when given a model
will produce a list of all the pages
and the names starting from the home
ending to the current location.
Oh, starting from the current location
ending to the home, which, whichever way
you, whichever way you want to use it.
That was, that, that part of the
program was kind of fun to code. I like,
I like that. And as I said, I
lifted a bar of this from the
ESOT site. There's quite a bit.
I, I feel that there's quite a bit
neat things on the ESOT that can be
done, that can, that can be used in
other systems. And I'll have to
use them on the L. There's a,
I like, like I said, earlier you
cannot use star system IDs,
planet IDs, basically self-defined
tags in the ESOT keys of the
dictionary, that's a limitation of the
end. That's a, I have had
couple of packs of, because of that,
because the, I have just a dictionary
with a key as an index, and the
index, of course, doesn't tell you
what it is used for, it's just a,
it's just a number. But
everywhere else in the program
performance, I'm not, I'm
trying to keep the use of primitive
data tags to the minimum instead.
So all the places where I'm talking
about planet, planet IDs, the
identification of planets, it's the
planet ID type, that is, that only
wraps a index, but it gives,
that wrapping gives the meaning to
the index, and it keeps,
you mixing the planet IDs, for example,
with the star system IDs, and
the same thing with the resources,
I talked about the resources on the
end, sorry, on the ESOT site,
and on the end of the end site,
there's a similar system. I couldn't
figure out if, if one can use
quantum tags, I think you cannot
yet, or will never be able to
but I still have a, I have, I still
can have a resources type that
has a three type of resources, the
biological resources, the
mechanical resources and the
chemical resources. So at least
I'm not going to mix biological
resources and mechanical resources
with this data. I might mix them
in a different context, in a way
that, for example, I would mix the
constructions speed with the
resource, with the
required amount of resources and
things like that, but still
I'm sort of happy with the resource
handling, and on the resource
handling is not, but this is
image and satellite resources
and raw resources that play
and uses to construct
things, and I'm very happy
how it's handled on the
end site. I probably
missed quite a bit while trying
to explain, but if something
else comes to mind, I'll record
a new episode and have a feeling
that if I keep working on this
game, it will, it will take
eights, it's like years and
years to get it to somewhere,
somewhat playable state, but
it's a fun project. I'm having
lots of fun trying to learn
the Haskell and Elm and
Lead Programming, and what not.
So I would be interested to
hear if you have any experiences,
experience on Elm, how you like
the language so far, it's a
relatively young language, and
if you have experience on the
Elm and some other of these
new languages like PureScript
or even some JavaScript
frameworks like React, and how
Elm, if you can talk about
the differences and the similarities
between them, I would be extremely
interested in hearing those on the
hack-up of the radio, but this is
too calm, this was quite a long
episode and tried to keep this a
little soul in the future, so
have a good day.
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