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F*: A general-purpose proof-oriented programming language(fstar-lang.org)
115 points by ducktective 8 hours ago | 44 comments
cyanregiment 6 hours ago | parent | next [-]

Clicked like 5 pages and never found 1 code example.

Idk why languages don't have their syntax in a sandbox front-and-center on the home page.

It's like a video game site with zero screenshots or videos (also rampant).

New programming languages I want 2 things:

1. What does the syntax look like

2. Why would I use this language

Talk about the proof logic, show the syntax, thank you

Verdex 5 hours ago | parent | next [-]

To borrow your video game analogy. F* is the dwarf fortress of programming languages. Screenshots are only going to confuse anyone who isn't ready to take a significant mental journey.

redrobein 20 minutes ago | parent [-]

This is needless fearmongering. F* looks a lot like F# code with semantics you should be familiar with if you've worked with other proof oriented languages. The website design is dated is all. The book gives exactly what the OP wants in the introductory chapter.

rixed 5 hours ago | parent | prev | next [-]

I'm the opposite: when landing in a programming language site I want to know the user case the authors had in mind, the memory model, the type system, the compilation targets, the data layout, the control structures, and only at the end just check that the syntax is not indentation based.

sroerick 5 hours ago | parent | next [-]

So I'm very seriously considering making my language indentation based. You're saying you wouldn't like that?

rixed 4 hours ago | parent | next [-]

No indeed I'm not a fan. I find it brittle and arbitrary for data values especially; that also makes automatic code generation and edition harder, for no good reason. But that's not an important consideration either way.

NuclearPM an hour ago | parent [-]

What is code edition?

aleph_minus_one 14 minutes ago | parent [-]

> What is code edition?

I think rixed means "code editing" (I guess that rixed is simply not a native (L1) or excellent L2 English speaker).

mcluck 2 hours ago | parent | prev | next [-]

For what it's worth, I love the semantics of many indentation based languages (F# for example) but really dislike editing them. Visually scanning is much easier with braces (imo) and it's much easier to navigate braced languages when using a vim-like editor

dunham 3 hours ago | parent | prev | next [-]

I don't mind indentation based languages. I used to hate them, but they've grown on me after using python, Haskell, Idris, Agda, etc. And I ended up making my own language indentation based (it is similar to Idris).

That said, it is hard-mode:

- You'll have to figure out how to parse it.

- If you want editor support, it's a pain to get tree-sitter to handle it.

- You may not be able to pull off editor operations like "rename" without implementing a pretty printer (a rename might affect indentation).

I think it is helpful for crude error recovery. On parse error, my language will simply skip to the next column 0 token and parse another declaration.

I did not do this (hindsight), but I would recommend arranging the grammar so you only get indented blocks in cases where the previous line ends in a keyword that introduces it. I think python has a trailing `:` every time indentation is introduced, and Elm does this too - in statements like `let` you need a newline after the `let` to get the multi-declaration version. (This addresses the rename issue.)

zlsa 5 hours ago | parent | prev | next [-]

I think this falls under "[wanting] to know the user case the authors had in mind"

BretonForearm 4 hours ago | parent [-]

There is no "user case", it's called use case.

aleph_minus_one 4 hours ago | parent [-]

> There is no "user case", it's called use case.

Perhaps English is not a native language for zlsa?

giancarlostoro 3 hours ago | parent | prev [-]

I love that people hate indentation based so I show them a poorly indented C style languages codebase to see how they feel about indentation.

koolala 3 hours ago | parent [-]

Isn't it easy to just auto format it?

NuclearPM an hour ago | parent | prev [-]

Use case. Not “user case”.

kasumispencer2 4 hours ago | parent | prev | next [-]

> Clicked like 5 pages and never found 1 code example.

But I clicked one (1) link to the online book and found a thousand?

giancarlostoro 3 hours ago | parent [-]

Should be on the home page of any programming language site.

kasumispencer2 3 hours ago | parent [-]

Is there actually any difference when it's just one (1) link away? Are most of us seriously this busy that we cannot spend even half a minute on this?

broken-kebab an hour ago | parent [-]

There's a difference, yes. How big it is isn't really relevant question cause its simply an unnecessary tax on visitors.

munchler 5 hours ago | parent | prev | next [-]

https://fstar-lang.org/tutorial/

_flux 5 hours ago | parent | next [-]

I guess it's a bit popular right now

    * Error 17 at Welcome.fst(24,0-28,30):
      - Could not start SMT solver process.
      - Command: ‘/home/site/wwwroot/fstar/bin/z3’
      - Exception:
          Unix.Unix_error(Unix.ENOENT, "create_process", "/home/site/wwwroot/fstar/bin/z3")
    
    1 error was reported (see above)
aleph_minus_one 5 hours ago | parent | prev [-]

> https://fstar-lang.org/tutorial/

FYI: The link to this tutorial is unluckily a little bit obscured on the F* website: Go to

> https://fstar-lang.org/index.html#learn (1)

and click on the image below the text "You probably want to read it while trying out examples and exercises in your browser by clicking the image below.".

In the section of (1) also the PDF version is linked:

> https://fstar-lang.org/tutorial/proof-oriented-programming-i...

cyanregiment 5 hours ago | parent [-]

I still don't see any code examples!

But I do see the editor to try it.

I wonder why more languages don't have a few simple examples of: "HTTP server", "hello world", "todo list app" that you can just click and it shows the code for how you'd make it in that language.

It matters a lot how the syntax looks IMO and seeing how, say, an API is scaffolded, helps understand a lot about the language in one glance

Edit: Page 18 of the PDF. That's the first time I found what the code looks like, thanks for sharing!

aleph_minus_one 4 hours ago | parent [-]

> I wonder why more languages don't have a few simple examples of: "HTTP server", "hello world", "todo list app" that you can just click and it shows the code for how you'd make it in that language.

Often the reason is that the value that the programming language brings is thinking very differently about how to write code - the examples how to write something in it are merely the "more boring" consequences of this different way of thinking.

--

If you want a programming language that "just" enables you to write something well-understood (in particular in the area of web development) like your suggested

> "HTTP server", "hello world", "todo list app"

in a perhaps just a little bit more elegant/concise way, just look at which web development language/framework is currently fashionable on HN.

cyanregiment 25 minutes ago | parent [-]

> just look at which web framework

See, by listing those, you can tell what it is.

I imagine the quick project showcase would be different for Swift or for Rust.

Would be nice to have something like that for this Fstar or any language I haven’t heard of - or maybe have but never looked into so I see why people are using it.

Like what kinds of things i can even think of writing with it - an implementation example

aleph_minus_one 17 minutes ago | parent [-]

> I imagine the quick project showcase would be different for Swift or for Rust.

> Would be nice to have something like that for this Fstar or any language I haven’t heard of - or maybe have but never looked into so I see why people are using it.

I suggest simply having a look at the table of contents of

> https://fstar-lang.org/tutorial/proof-oriented-programming-i...

This in my opinion gives you a first rough idea for what kind of problems people are using F*.

Spoiler alert: these are not the kind of problems which are related to ["HTTP server", "hello world", "todo list app", ...].

This is exactly the reason why I wrote further above:

> Often the reason [why more languages don't have a few simple examples of: "HTTP server", "hello world", "todo list app"] is that the value that the programming language brings is thinking very differently about how to write code - the examples how to write something in it are merely the "more boring" consequences of this different way of thinking.

cyanregiment 3 minutes ago | parent [-]

> these are not the kind of problems which are related to ["HTTP server", "hello world", "todo list app", ...].

Ok, what kinds of problems are they?

And ideally - what does a simple solution look like in F-star?

Set me on the path to installing the thing (ideally above the fold)

summarity 21 minutes ago | parent | prev | next [-]

What? There’s literally a completely interactive book linked right from the home page.

rainyq 6 hours ago | parent | prev | next [-]

just click the screenshot

cyanregiment 5 hours ago | parent [-]

Takes you to an empty editor with still no code examples

remywang 4 hours ago | parent | prev | next [-]

That’s because syntax is the least interesting part of F*.

thomastjeffery 4 hours ago | parent [-]

Then why are we all so interested?

Examples provide more than syntax. It's the semantics that we care about most.

aleph_minus_one 4 hours ago | parent [-]

> Examples provide more than syntax. It's the semantics that we care about most.

... and this semantics is explained in a quite encompassing way in the introductory notes "Proof-Oriented Programming in F*":

> https://fstar-lang.org/tutorial/proof-oriented-programming-i...

> https://fstar-lang.org/tutorial/

voodooEntity 3 hours ago | parent | prev | next [-]

Thank you ! I just had the absolute same experience and was about to write a similar comment - take my upvote instead !

qzzi 5 hours ago | parent | prev [-]

I clicked on 2 links on the main page in the Learn F* section...

LelouBil 7 minutes ago | parent | prev | next [-]

[delayed]

LelouBil a minute ago | parent [-]

[delayed]

pvsnp 6 hours ago | parent | prev | next [-]

I liked being able to express calling external libraries while incrementally migrating existing C codebases to F*. Very solid language.

rixed 4 hours ago | parent [-]

What do you mean "express calling"? You mean calling the former C versions of the functions not yet ported, while asserting their behavior?

boutell an hour ago | parent | prev | next [-]

I guess responsive stylesheets can't be implemented without side effects...

3lambda 5 hours ago | parent | prev | next [-]

Would this language be useful for implementing compilers and formally proving things about them?

physPop an hour ago | parent [-]

yes thats the main reason, agda , coq similar ideas

IshKebab 4 hours ago | parent | prev [-]

F* seems to be a collection of like five different languages and proof systems. Honestly I never figured it out.

Does it get basic stuff like subtraction and u8 right, unlike Lean?