Wisp: Small-but-featureful embeddable Lisp interpreter written in Haskell | Hacker News Reader

Wisp: Small-but-featureful embeddable Lisp interpreter written in Haskell

github.com

73 pointsluu25 comments

    > wisp lives in the ST (optionally IO) monad. separate 
    > interpreters with completely segregated environments can be 
    > run concurrently. wisp has a few IO facilities, but they're 
    > completely sandboxed and can't accidentally affect the host 
    > program or environment.

This is wonderful. There's already an embedded R5RS Scheme for Haskell (http://hackage.haskell.org/package/husk-scheme) but it runs everything in the IO monad. That makes it fairly annoying for sandboxed embeddings.

Apart from its use of ST rather than IO, I'm curious how else Wisp compares to Husk. As far as I can tell, despite the name, Wisp appears to be a Lisp-1 (single namespace for functions and variables, no need to call "apply" or similar on variables referencing functions to call them).

Not to be confused with Wisp: Homoiconic JS with clojure syntax, s-expressions and macros: https://github.com/Gozala/wisp

Or my: https://github.com/espringe/wisp (Whitespace lISP) with f-expressions!

You might like my whitespace lisp with f-expressions: http://akkartik.name/blog/wart

Incidentally, why is the scala version 100x slower than the Haskell one?

Does anyone have any good, language agnostic resources for writing interpreters (not just for lisp)?

Functional or imperative language?

/r/compilers [1] has some good resources. You can also check its top submissions [2].

I also recently found Matt Might's Compilers class [3] via a submission here on HN. It has a lot of language-agnostic resources.

[1]: http://www.reddit.com/r/compilers

[2]: http://www.reddit.com/r/compilers/top/

[3]: http://matt.might.net/teaching/compilers/spring-2013/

For a quick introduction this might be worth a look (not really language agnostic though) http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_H...

https://github.com/apsk/hlisp Another lisp in haskell

I pine for a Lisp with the embeddable ease of Lua.

Guile?

http://www.gnu.org/software/guile/

Unfortunately, Guile is both larger, and less portable than Lua. It's also licensed under the LGPL, which is harder (or impossible) to use in some environments than Lua's MIT-like license.

It could be trivially implemented in Lua as a pre-processor. Lua has lambdas, higher level functions, lexical scope and tail call elimination.

The main problem is that it doesn't have a ternary operator, making conditional expression problematic to represent (you have to wrap an if statement in a lambda called on the fly).

For something more fully featured, see [0], it is written in MoonScript (which itself compiles to Lua), and the parser depends on LPeg, but writing a S-expression parser is rather easy.

Edit: There's also lcl [1], which is implemented in C. Written by lhf, one of the Lua authors. From the test files, it looks very basic.

[0] https://github.com/leafo/moonlisp/tree/master/lisp

[1] http://www.drdobbs.com/open-source/lua-an-extensible-embedde...

Wrapping an if in a lambda is unlikely to work as expected.

    ((if foo + -) 4 6)

Can be compiled to

    (function()
        if foo then return plus
        else return minus
        end
    end)()(4, 6)

It is far too verbose to be used in manually crafted Lua, but acceptable if you treat it as a compiler target (with the caveat that the lambda creation will prevent LuaJIT from JITting that piece of code).

Plug https://github.com/meric/l2l

"A object-oriented, unicode-enabled lisp that compiles to and runs as fast as Lua. Equipped with macros and compile-time compiler manipulation. Comes with all built-in Lua functions."

Nice one! I started coding one after writing the above comment.

I have a question regarding your implementation: why do you use `goto`s rather than `elseif` to compile `(cond)` blocks? For nested blocks?

Oh I think it it was for the return value of cond.

ChibiScheme (https://code.google.com/p/chibi-scheme/) tries to be that. I've considered using it but have avoided it due to its relative newness and a few portability issues.

Lysp (http://piumarta.com/software/lysp/) is fairly close to what I'm guessing you're "pining" for and if not, hey it's open source so have at it!

Lysp uses a lot of non-standard (and rarely implemented) extensions, and so would be very hard to use in most places.

The author's own Maru (http://piumarta.com/software/maru/) might be better suited for this, but I'm not sure..

Alex Shinn's Chibi scheme, weighing in at 50kB (but with a dependency on the Boehm garbage collector, which weighs >1 Mb ...), might fit the bill.

Some links

1. Andy Wingo (main Guile implemetor)'s "buyer's guide" to Scheme implementations - http://wingolog.org/archives/2013/01/07/an-opinionated-guide...

2. Chibi Scheme homepage - http://synthcode.com/scheme/chibi/

There's also Chicken Scheme.

While maybe not as tiny as Lua, it is designed to be embeddable out of the box.

The FFI is very simple.

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