Welcome to the Lounge

27-Dec-23 2:44

Bear with me, because as much as I am loath to holy roll about technology, I still have my peeves.

I went about porting my DFA lexer engine from C# to TypeScript. It was primarily an exercise in teaching myself TypeScript, plus brushing up on my JS.

So I implement the bones of it, and after adjusting my mental map to the JS way of doing things I got it mostly working.

Then I went about trying to use a Map keyed by Sets.

Turns out JS Map and Set will only compare by value for "scalar" types (presumably including strings) or otherwise it uses reference comparisons. You can't override your own equality mechanism either.

how to customize object equality for javascript set - Stack Overflow[^]

Consequently, there is no performant way to do subset construction to convert an NFA to a DFA in this language.

I've seen others solve this problem by using string keys, but this falls down for machines of non-trivial size.
Regex FA visualizer[^] is one example but I can basically crash it or stall it out for a long time at least with any non-trivial expression. This one also doesn't work properly besides, but I have no other link handy for you to try.

This may be academic, but it is also basic computer science. A language should be able to allow you to implement computer sciencey algorithms and constructs - especially those that have been adapted to countless other programming languages. DFA by subset construction is basic.

And you can't do it in JS.

I can't even begin to imagine what LALR table generation would look like.

You may be wondering why do I care?

Because node.js.
Because Angular
Because React-Native

it's not just for web front ends anymore. JS is an almost virulent technology these days. It needs to be, if not Turing complete at least cover the fundamentals, or you're just spreading garbage around.

Without a way to do custom comparisons at the very least on hashed containers, your language isn't going to be able to do a lot of things other high level languages can accomplish handily.

Is it even a "real" language? Is it ready for primetime, or is it just being adopted because we can? Unsure | :~

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

modified 27-Dec-23 9:13am.

Gary R. Wheeler27-Dec-23 3:15

Gary R. Wheeler

27-Dec-23 3:15

My experience has been that programming languages evolve mostly to meet practical needs. You can substitute the words economic or business for the word practical and still have a valid statement. While there is a certain amount of 'need' for the ability to implement computer-sciencey algorithms in a language in a performant way, I think it's a lower priority than other features that simplify or extend expression of common idioms.

honey the codewitch wrote:
Consequently, there is no performant way to do subset construction to convert an NFA to a DFA in this language

I take it that it's not impossible, and your objection is to the performance of the implementation required by the language? It sounds like an edge case you run in to with almost every language that needs an alternative solution.

For example: Since you're implementing this in TypeScript, it's a web app. That implies a server. What about serializing the NFA, shipping it to the server for conversion, and deserializing the DFA returned? 'Out-of-the-box', as it were Big Grin | :-D

Software Zen: delete this;

honey the codewitch27-Dec-23 3:52

27-Dec-23 3:52

TypeScript (JS really in this case, since TS is just syntactic sugar and validation) doesn't imply a web app anymore, which was part of the point I was making in my original, arguably too verbose post.

It's used on the backend (node.js). It's used on the desktop (angular, react-native). Kevin only knows where next?

My concern is it doesn't seem ready for it.

As far as computer sciencey algorithms not being needed, consider that constructs in computer science make up nearly every programming problem you'll ever solve.

DFA by subset construction is not the only place you'd ever need custom equality.

From ECMAScript 6: maps and sets[^]

5.2 Why can’t I configure how maps and sets compare keys and values?

Question: It would be nice if there were a way to configure what map keys and what set elements are considered equal. Why isn’t there?

Answer: That feature has been postponed, as it is difficult to implement properly and efficiently. One option is to hand callbacks to collections that specify equality.

Another option, available in Java, is to specify equality via a method that object implement (equals() in Java). However, this approach is problematic for mutable objects: In general, if an object changes, its “location” inside a collection has to change, as well. But that’s not what happens in Java. JavaScript will probably go the safer route of only enabling comparison by value for special immutable objects (so-called value objects). Comparison by value means that two values are considered equal if their contents are equal. Primitive values are compared by value in JavaScript.

Read that carefully and you'll see the problem is more fundamental than simply maps and sets. You can't override equality. You can't implement custom value equality for objects.

That hamstrings your ability to use Sets and Maps in the first place, but that's not the only place it limits you.

It also speaks to a large issue of - if this is missing/incomplete/problematic-to-implement based on how the language works under the covers, what else can't it do that is fundamental?

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Gary R. Wheeler27-Dec-23 4:30

Gary R. Wheeler

27-Dec-23 4:30

honey the codewitch wrote:
As far as computer sciencey algorithms not being needed, consider that constructs in computer science make up nearly every programming problem you'll ever solve.

I was trying to express the notion that the ability to implement algorithms efficiently depends upon the utility of that algorithm in the target environment.

honey the codewitch wrote:
Read that carefully and you'll see the problem is more fundamental than simply maps and sets. You can't override equality. You can't implement custom value equality for objects.

My knowledge of TypeScript/JavaScript is limited. Would it be possible re-implement maps and sets that supported at least a limited form of the capabilities you require?

honey the codewitch wrote:
if this is missing/incomplete/problematic-to-implement based on how the language works under the covers, what else can't it do that is fundamental?

There's the key word (no pun intended).

Software Zen: delete this;

honey the codewitch27-Dec-23 4:36

27-Dec-23 4:36

Gary R. Wheeler wrote:
I was trying to express the notion that the ability to implement algorithms efficiently depends upon the utility of that algorithm in the target environment.

Okay, fair enough. Though again, I'm still worried about this given this is my first attempt to do something non-trivial with typescript, or even - in years - javascript. The first attempt, and I run into such a fundamental and showstopping limitation it definitely gets the hair on the back of my neck on end, you know?

Gary R. Wheeler wrote:
My knowledge of TypeScript/JavaScript is limited. Would it be possible re-implement maps and sets that supported at least a limited form of the capabilities you require?

Not efficiently using JS itself, as far as I can tell. I haven't profiled to be sure, but it's a lot of work for something that probably won't solve the issue.

Gary R. Wheeler wrote:
There's the key word (no pun intended).

Which brings me back to me above response, about this being my first real go at TS, and my first time running into a major wall with it. It doesn't bode well at least to me.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

jschell27-Dec-23 5:52

27-Dec-23 5:52

honey the codewitch wrote:
if an object changes, its “location” inside a collection has to change, as well. But that’s not what happens in Java. JavaScript will probably go the safer route of only enabling comparison by value for special immutable objects (so-called value objects).

I realize that is not your statement but I will note it is a silly response.

In ANY language if you change the contents of a entities within a collection there is a risk that you violate the constraints of the collection.

Any competent programmer that actually understands a Java HashMap (and similar) must understand the impact of attempting to change the semantics of what equals() and hashcode() actually means.

I can see a Junior developer doing that.

I can also see a Junior developer failing to correctly manage memory allocations in C/C++ also.

But Java is not JavaScript nor are either C/C++.

honey the codewitch wrote:
But that’s not what happens in Java

That is perhaps more ludicrous. Is there any language where that happens?

honey the codewitch27-Dec-23 6:30

27-Dec-23 6:30

I agree with you about that response. It seems like they refuse to implement the feature until they can overengineer it.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

MSBassSinger28-Dec-23 4:08

MSBassSinger

28-Dec-23 4:08

Quote:
It's used on the backend (node.js). It's used on the desktop (angular, react-native).

That is just bad application design. JavaScript on the backend or the desktop is like putting a lawnmower engine in a Chevy Corvette and expecting to get a speeding ticket on the Interstate.

C#, VB.NET, Java/Kotlin, Rust, Python, etc. are much better server-side and desktop languages than JavaScript.

hpcoder218-Jan-24 13:59

hpcoder2

18-Jan-24 13:59

Big one for me - lack of destructors or finalisers.

honey the codewitch18-Jan-24 14:07

18-Jan-24 14:07

I've gotten so used to garbage collection that I've learned to accept it. I don't like it but it's no longer a huge deal for me.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

hpcoder218-Jan-24 14:43

hpcoder2

18-Jan-24 14:43

It's not a matter of garbage collection. Java, C# and even Python have finalisers that support adding code that is executed when an object is reaped by the GC. This becomes essential when providing a C++ implementation of an object in the target language (say via Emscripten) to arrange for the C++ destructor to be called when the owning object is destroyed by the garbage collector.

Lack of finalisers mean the C++ implementation is limited to PODs (plain ordinary data types), whcih is pretty damn limiting.

honey the codewitch18-Jan-24 14:44

18-Jan-24 14:44

That's fair enough. I didn't realize that limitation of emscripten.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Daniel Pfeffer27-Dec-23 4:52

Daniel Pfeffer

27-Dec-23 4:52

IMO, any computer language that is Turing-complete is a "real" computer language. As it is possible to implement a Turing machine in JavaScript, it is a "real" computer language.

JavaScript is undoubtedly not the best language for implementation of certain algorithms, but one can find non-performant examples of algorithms in almost any language.

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

0x01AA27-Dec-23 5:30

0x01AA

27-Dec-23 5:30

I have long dreamed of a universal 'meta language' to describe a task.
And of course also then, 'simply' writing tools that converts this 'meta language' into the currently available tools.
I think this is pretty much on your wavelength with parsers, whatever...

modified 27-Dec-23 11:42am.

jschell27-Dec-23 5:56

27-Dec-23 5:56

Myself I am waiting for that self conscious highly intelligent robot butler which is self repairing and runs for a thousand years on its internal power source.

Then I could just tell it to do my job for me. And clean the kitchen.

Perhaps also to chase me around the house with a stick so I get enough exercise too.

0x01AA27-Dec-23 6:02

0x01AA

27-Dec-23 6:02

Not sure, but you answer with irony? But what I have in my mind is the next step from compiler-compiler

jschell28-Dec-23 5:45

28-Dec-23 5:45

0x01AA wrote:
long dreamed of a universal 'meta language'

It cannot exist.

That is why so many languages exist. Reasons vary but in general a need was not being met or the newer one was supposed to be better.

If anything you can look to the many languages that use the Java VM and yet they are not Java. That is not the only language platform where other languages were built on it.

jschell27-Dec-23 5:42

27-Dec-23 5:42

honey the codewitch wrote:
I went about porting my DFA lexer engine from C# to TypeScript

Just noting that javascript has a very feature rich regular expression support.

honey the codewitch wrote:
allow you to implement computer sciencey algorithms and constructs

Your description is incomplete. From what I read in your comment it does allow you to do it.

It just is not as fast as you like/want.

honey the codewitch wrote:
is one example but I can basically crash it or stall it out for a long time at least with any non-trivial expression.

Perhaps this is your basis? Without having looked at that solution at all, I can only note that being Turing complete does not mean that the language has no bounds. That is not part of the description. And all languages would fail at that.

honey the codewitch wrote:
or is it just being adopted because we can?

I know a business that was sold for quite a bit of money which ran high performance high volume real time data processing using javascript.

Not the platform I would choose and I don't know what hardware costs were. But they certainly did it some how.

I doubt most others would choose that also. For complex systems one often uses a mix of technologies.

honey the codewitch27-Dec-23 6:29

27-Dec-23 6:29

jschell wrote:
Just noting that javascript has a very feature rich regular expression support.

Can't lex, and won't fulfill the project requirements, which are "learn typescript"

jschell wrote:
Your description is incomplete. From what I read in your comment it does allow you to do it.
It just is not as fast as you like/want.

There is a point where something takes too much time and space to be practical. That is a real thing. That is the issue here.

So no, it's not "just not as fast as I'd like", it is not usable.

jschell wrote:
Perhaps this is your basis? Without having looked at that solution at all, I can only note that being Turing complete does not mean that the language has no bounds. That is not part of the description. And all languages would fail at that

It's not. Really none of this is relevant.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

jschell27-Dec-23 6:39

27-Dec-23 6:39

honey the codewitch wrote:
which are "learn typescript"

lol...well yes that doesn't work.

honey the codewitch wrote:
There is a point where something takes too much time and space to be practical. That is a real thing.

At least with regular expressions, in general (so perhaps not your solution, or could be) it is possible to create ones that will never end. Or will take days to complete.

So that by itself is not a determinate.

honey the codewitch27-Dec-23 6:49

27-Dec-23 6:49

This isn't even to run the expression, just to turn it into a state machine.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix