Show HN: A Lisp compiler and environment in Go

[eatonphil]

https://github.com/gsp-lang/gsp

[jgalt212]

Along these lines, do people here think porting Clojure to use the Go VM a worthwhile endeavor?

Or, to the contrary, if one just wants to avoid the JVM, would it just be better to write Clojurescript?

That being said, having one binary to distribute and install is a very strong argument for Go VM languages.

[kimi → jgalt212]

That's what I thought. Clojure is a "parasitic" language, meaning that it is meant to work with a host, so it should not be too hard to make it work with a Go environment. Plus, the fact that there is a very well working ClojureScript means that any "hard" deps on the JVM's original implementation should be gone. Clojure is a sweet language to work in, but you just cannot create a small executable out of it.

[kimi → jgalt212]

To clarify: I have been looking for something along these lines because my company is looking to invest heavily into Clojure. We come from a Java/JVM environment, and we are very happy with it, but we have to ship a "beacon" to appliances. This means: Java on the server, GWT or JavaScript on the browser, and perl/C on the beacon. With Clojure / ClojureScript / ClojureGo we could have the same programmers moving between the three environments, and it would be a major win for us. Clojure might not be perfect, but we still would be able to write any critical code in the host language.

[wtetzner → jgalt212]

I wasn't aware there was a Go VM.

[tptacek → wtetzner]

There isn't, of course, but if you mentally substitute "runtime" for "VM", the question is perfectly valid.

[anjanb → tptacek]

In this context, what's the difference between a "runtime" and a "VM" ? What does a "VM" have in addition to a "runtime" ?

[wolf550e → anjanb]

https://en.wikipedia.org/wiki/Runtime_system

libc is a runtime, but not a VM.

[tptacek → wolf550e]

Also compiler calling conventions, the memory map, program initialization, the GC subsystem...

[howeyc]

Interesting, looks almost like how you'd write Go using S-expressions. Seems like you have access to the stdlib from the examples. I wonder if you could use other Go libraries. I also wonder if you can use co-routines or channels.

This[1] allows you to write something resembling Scheme R5RS but with some Go extras like channels/co-routines, but no access to Go's stdlib.

[1] https://github.com/kedebug/LispEx

[eatonphil → howeyc]

You should be able to reach any Go library, in fact. Aside from the Prelude, the Gsp Stdlib[0] is in fact just bindings to the Go stdlib that casts every value from interface{} into the required type. You can make bindings to any other library in this manner.

I do not know why Go-routines would not work, though I have not tried yet.

Another difference from the lisp you brought up (and the one I'm more familiar with, glisp[1]) is that Gsp is compiled as opposed to interpreted. This would ostensibly have speed features.

I am interested to test how this fares compared to these other Go Lisps and Clojure.

[0] https://github.com/gsp-lang/stdlib

[1] https://github.com/zhemao/glisp

[current_call]

Wouldn't it be easier to just work in the reverse direction?

https://github.com/zkat/chanl

[steveklabnik → current_call]

It might be easier, but showing both directions is still very cool.

[e12e]

It may be a naive quesiton, but what does "prelude" mean in this context? I get that I can use this to emit go code from gisp, and compile that. But the example under the heading "using the prelude" doesn't really tell me anything. Looking at the code, it appears to define a lot of basic lisp stuff -- but without all that, how does gsp work in the first place?

Is it simply the difference of wrapping things up so that they... work?:

    diff <(gsp hello.gsp) <(gisp hello.gsp)
    4,7c4,5
    <       "github.com/gsp-lang/stdlib/fmt"
    <       "github.com/gsp-lang/gsp/core"
    <       "github.com/gsp-lang/stdlib/prelude"
    <       "github.com/gsp-lang/stdlib/net/http"
    ---
    >       "/fmt"
    >       "/net/http"
    18,19d15
    < 
    < var _ = prelude.Len

As far as I can tell, gisp doesn't produce go code that can be compiled. But what good is the go code gisp produces? Can/should it be saved to file and imported into another go program?

[eatonphil → e12e]

I'm not sure what gisp you are running. The gsp program adds some imports by default (including the prelude). On the other hand, jcla1's gisp definitely does not include these files unless you do so manually in the .gsp file.

[e12e → eatonphil]

As far as I know, that's "regular gisp (rm $(command -v gisp); go get -u github.com/jcla1/gisp), and the full hello.go it produces is:

cat hello.gsp (ns main "/fmt" "/net/http")

    (def hello (fn [w r]
      (fmt/fprintf w "hello")
      ()))

    (def main (fn []
      (http/handle-func "/" hello)
      (http/listen-and-serve ":8080" nil)))

gisp hello.gsp

    package main

    import (
            "/fmt"
            "/net/http"
    )

    func hello(w, r core.Any) core.Any {
            fmt.Fprintf(w, "hello")
            return nil
    }
    func main() {
            http.HandleFunc("/", hello)
            http.ListenAndServe(":8080", nil)
    }

(Which go won't compile due to errors with imports, missing core.Any etc).

I realize hn isn't the best place to discuss issues, but if anyone have played with gisp, and could shed some light (eg: maybe gisp is go 1.4 only?) that'd be great.

Incidentlially gsp/gspc seems to work as intended. Maybe I'm misunderstanding the purpose of gisp?

[eatonphil → e12e]

I think you are just having path issues. Also, you are using a gsp example to test gisp. There are a few shorthands that gsp supports that gisp does not - such as imports starting with /. Gisp will not resolve these.

If you continue to have issues and want to get it working correctly, feel free to email me.

[e12e → eatonphil]

Thank you four your reply. I had my suspicions that might be the issue (the shorthand/differences between gsp/gisp in particular). I also played a bit with the simple factorial example[f] from gisp -- which apparently doesn't work with gps(c) (gisp apparently allows calling casts as functions [eg: (int ImNotAnIntButAfloat)] -- looks like gsp chokes on that.

After some tweaking I couldn't get [f] to work with gsp (but it worked fine with gisp + go build). Looks like both projects could use some more (esp. motivating) examples, and maybe a little more introduction/documentation. At least enough to encourage play :-)

[f] https://github.com/jcla1/gisp/blob/master/examples/factorial...

[eatonphil → e12e]

Good call with the casting issue. I'd been seeing that that wasn't working correctly but I just now figured it out.

Gisp lacked the ability to have function arguments actually be functions themselves. Gsp gets around this by casting __all__ (a lazy move, I know) functions to interface{} then to func([arg core.Any]+) core.Any.

I do stop this behavior for a certain whitelist - I need to add int/float64/bool/string to that list I think.

This was definitely just a first step. I think getting the Prelude to work is by far the coolest part. It did actually take a lot of trial and error hacking gisp -> gsp to get it working.

After this I will probably look into self-hosting documentation and maybe a cookbook.

[e12e → eatonphil]

Good to hear :-)

Btw, I'm still not sure what "prelude" means in this context...

[deadprogram]

This looks very interesting...