For Common Lispers such as myself, who are vaguely aware of developments in the Scheme space: the most important difference between CRUNCH and Chicken appears to be that, while both compile down to C/object code, CRUNCH is additionally targeting a statically-typed subset of Scheme.
Opinion: this is great. The aversion of Lispers to static types is historical rather than intrinsic and reflects the relative difference in expressiveness between program semantics and type semantics (and runtime vs tooling) for much of computing. Now that types and tools are advancing, static Lisps are feasible, and I love that.
I don't believe it's not intrinsic. A lot of the reason why Lispers may be averse to static types is because of the perceived inflexibility it can induce into the system. Lisp programmers don't want to be told what to do, especially by the compiler. Some CLs like SBCL have allowed some form of inference through the standard type declarations in the language. This leads me to believe that the 'right thing' in the case of Lisp is a combination of dynamicity and some stronger typing features that can be applied during the optimization stage. The dynamic nature and ease of use of Lisp relative to its performance is one of its greatest assets: it would be nearsighted to try and sacrifice that--a good Lisp programmer can optimize the important parts of his programs such that they're comparable to or even outperform their equivalents in other more ``high-performance'' languages. With that being said, these developments might bring us closer to a ``sufficiently smart compiler'' that could make that latter stage mostly unnecessary.
> A lot of the reason why Lispers may be averse to static types is because of the perceived inflexibility it can induce into the system.
This perceived inflexibility is what my comment was getting at - that for primitive type systems available back in the 80's, yes, the types significantly constrained the programs you could write. With today's type systems, however, you have far more flexibility, especially those with "Any" types that allow you to "punch a hole in the type system", so to speak.
When I tried typed Python a few years ago, I found out that, to my surprise, 99% of the code that I naturally wrote could have static types attached (or inferred) without modification because of the flexibility of Python's type system.
I also learned that types are a property of programs, more than just languages. If a program is ill-typed, then having a dynamically-typed language will not save you - it will just crash at runtime. Static types are limiting when either (1) they prevent you from writing/expressing well-typed programs because of the inexpressiveness of the type system or (2) it's burdensome to actually express the type to the compiler.
Modern languages and tools present massive advances in both of those areas. Type systems are massively more expressive, so the "false negative" area of valid programs that can't be expressed is much, much smaller. And, with type inference and more expressive types, not only do you sometimes not have to express the type in your source code at all (when it's inferred), but when you do, it's often easier.
The "Any" type is really what steals the show. I don't think that there's a lot of value in a fully statically-typed Lisp where you can't have dynamic values at all - but I think there's a lot of value in a Lisp with a Python-like type system where you start out static and can use "unknown", "any", and "object" to selectively add dynamic types when needed.
Because, being a Lisper, you probably think like me, I'll give you the idea that really convinced me that types are positive value (as opposed to "only" being small negative value): they enable you to build large, complex, and alive systems.
Types are a force-multiplier for our limited human brains. With types, you can more easily build large systems, you can more easily refactor, you can start with a live REPL and more easily transition your code into source on disk. Types help you design and build things - which is why we use Lisps, after all!
I don't think it makes sense to conflate Lispers to Schemers. I've programmed in both languages but have a stronger affinity for Scheme partially because semantically it is less flexible and more "staticy" than Lisp. Philosophically, the languages tend to attract different personalities (to the extent that the highly fragmentary Scheme world can be characterized).
I want static types in a higher level assembly language for systems programming. That's because I want to work with machine-level representations, in which there are no spare bits for indicating type at run-time (moreover, using such a language, we can design a type system with such bits, in any way we please).
I don't want static types in a high level language.
It's just counterproductive.
We only have to look at numbers to feel how it sucks. If we divide two integers in Common Lisp, if the division is exact, the object that comes out is an integer. Otherwise we get a ratio object. Or if we take a square root of a real, we get a complex number if the input is negative, otherwise real.
This cannot be modeled effectively in a static system. You can use a sum type, but that's just a greenspunned ad hoc dynamic type.
> Now that types and tools are advancing, static Lisps are feasible, and I love that.
Haven't that been feasible for a pretty long time already? Judging by how well-received (or not) they've been, it seems there isn't much demand for it. Things like clojure.spec and alike (compile-time + run-time typing) seems much more popular, but isn't static.
Type inference is probably the biggest thing. You would need explicit "phases" to expand macros, disallow macro expansion at runtime, and implement bi-directional type inference HM-style to get even close to what OCaml has.
To be honest, I'd kill for a Lisp that had the same type system as OCaml, but I suspect the closes we'll get is basically Rust (whose macro system is quite good).
The interesting part is how few trade-offs had to be made to make GC-less (ref-counting) Scheme-to-C compilation attainable, and how closely CRUNCH adheres to R7RS.
Notable is the lack of call/cc, but in my "armchair expert" opinion, it's the ugliest part of the language. Yes, continuations as a first-class object are elegant and succinct, but in order to do anything actually useful with them (like implementing exceptions), you need library code, which makes them much less composable.
I think there's a much more pleasant and practical language lurking somewhere between R6RS "big" and traditional "small" Scheme, but I feel it would take a BDFL to flesh it out.
This just made my day. I'm the author of Scheme for Max, an extension to the Max music programming environment that puts the s7 Scheme interpreter in it for scripting note-event level code (not dsp). It would be fantastic to also be able to use a subset of Scheme for generating DSP level code, where speed would be more important than dynamic typing or continuations/tco/etc.
Fun fact: the DOS version of the Cakewalk music software in the late 80's had a scripting language (CAL) that was very loosely based on Lisp. The author (Greg Hendershott) later went on to write a lot about Lisp.
Yes! This was the first "lisp" I ever used, back in the very early 90's. It was still part of Cakewalk in the windows releases at that time and was really Cakewalk's secret weapon.
With the Ableton Live Notes API, enabling something similar is one of the things I plan on adding to Scheme for Max this year.
Thanks for the tip about who wrote it, I will look him up!
I'm glad to see more projects exploring the statically compiled Scheme space. One difference from PreScheme listed is R7RS conformance, but the PreScheme restoration project is also targeting R7RS so that the compiler is portable to many Scheme implementations. The biggest difference I can see is manual memory management vs. reference counting. Though, one of the TODO items for the PreScheme restoration is to revisit memory management. Maybe PreScheme will end up with reference counting, as well.
The popcount example does compile, if you drop the "assume" form,
(import (chicken bitwise) (chicken fixnum))
(define (popcount32 x) ; From "Hacker's Delight"
; (assume
(let ((x (fx- x (bitwise-and (arithmetic-shift x -1) #x55555555))))
(let ((x (fx+ (bitwise-and x #x33333333)
(bitwise-and (arithmetic-shift x -2) #x33333333))))
(let ((x (bitwise-and (fx+ x (arithmetic-shift x -4)) #x0F0F0F0F)))
(let ((x (fx+ x (arithmetic-shift x -8))))
(let ((x (fx+ x (arithmetic-shift x -16))))
(bitwise-and x #x0000003F)))))))
Turns into somewhat redundant C, looks much like transliterated bytecode, e.g.
> Other targets are possible, like GPUs. I don't know anything about that, so if you are interested and think you can contribute, please don't hesitate to contact me.
The freestanding macro suggests most of the heavy lifting is done. Stuff the GPU targets will struggle with in no particular order:
- setjmp / longjmp
- signals (if used?)
- threads
- fast alloc/free
- stack will be smaller than chicken expects
I don't know how to do signals. The rest are merely difficult.
I thought chicken used it to treat the C stack as an arena for the GC, with longjmp acting as part of garbage collection. I don't see how it would help for call/cc, that needs a reified stack to handle repeat invocations.
so if I understand this right, it could be a way to run scheme on esp32 and similar microcontrollers, isn't it?
Also its small size would make it a perfect target to compile to typescript/deno/wasm without rejecting the s-exp power and runtime possibilities in its full chicken code at the backend...
Not a scheme, but for running a lisp on microcontrollers uLisp is pretty amazing. http://www.ulisp.com/
You even get a REPL and everything WHILE running on the hardware. Super easy to set up and get going. Though as it is interpreted so you will of course not have native performance. Still very useful for prototyping and hobbyist projects.
As a rule, interpreted code has a smaller memory footprint than natively compiled programs.
Even interpreted on a several hundred MHz classic RISC microcontroller, Lisp will chew through a million cons cells a second or more - an order of magnitude or so faster than the old Lisp machines in the 80s were and they used to run giant CAD systems on those to design aircraft and stuff. (Albeit slowly...)
OTOH if you want something that gives you a REPL and everything directly on the hardware but is also not as slow as your typical interpreter, look at Forth.
It's compiling a subset of Scheme that can be statically typed. It's not for full-blown live-hackable Scheme programs. You'd use Crunch or PreScheme to implement things that you can't implement in Scheme, like a garbage collector. I don't know if Crunch has this feature, but with PreScheme you can run your PreScheme programs at the Scheme REPL so you can have your comfy REPL-driven dev environment and then create a static executable when you're ready.
Readit News
Opinion: this is great. The aversion of Lispers to static types is historical rather than intrinsic and reflects the relative difference in expressiveness between program semantics and type semantics (and runtime vs tooling) for much of computing. Now that types and tools are advancing, static Lisps are feasible, and I love that.
This perceived inflexibility is what my comment was getting at - that for primitive type systems available back in the 80's, yes, the types significantly constrained the programs you could write. With today's type systems, however, you have far more flexibility, especially those with "Any" types that allow you to "punch a hole in the type system", so to speak.
When I tried typed Python a few years ago, I found out that, to my surprise, 99% of the code that I naturally wrote could have static types attached (or inferred) without modification because of the flexibility of Python's type system.
I also learned that types are a property of programs, more than just languages. If a program is ill-typed, then having a dynamically-typed language will not save you - it will just crash at runtime. Static types are limiting when either (1) they prevent you from writing/expressing well-typed programs because of the inexpressiveness of the type system or (2) it's burdensome to actually express the type to the compiler.
Modern languages and tools present massive advances in both of those areas. Type systems are massively more expressive, so the "false negative" area of valid programs that can't be expressed is much, much smaller. And, with type inference and more expressive types, not only do you sometimes not have to express the type in your source code at all (when it's inferred), but when you do, it's often easier.
The "Any" type is really what steals the show. I don't think that there's a lot of value in a fully statically-typed Lisp where you can't have dynamic values at all - but I think there's a lot of value in a Lisp with a Python-like type system where you start out static and can use "unknown", "any", and "object" to selectively add dynamic types when needed.
Because, being a Lisper, you probably think like me, I'll give you the idea that really convinced me that types are positive value (as opposed to "only" being small negative value): they enable you to build large, complex, and alive systems.
Types are a force-multiplier for our limited human brains. With types, you can more easily build large systems, you can more easily refactor, you can start with a live REPL and more easily transition your code into source on disk. Types help you design and build things - which is why we use Lisps, after all!
I don't want static types in a high level language.
It's just counterproductive.
We only have to look at numbers to feel how it sucks. If we divide two integers in Common Lisp, if the division is exact, the object that comes out is an integer. Otherwise we get a ratio object. Or if we take a square root of a real, we get a complex number if the input is negative, otherwise real.
This cannot be modeled effectively in a static system. You can use a sum type, but that's just a greenspunned ad hoc dynamic type.
Haven't that been feasible for a pretty long time already? Judging by how well-received (or not) they've been, it seems there isn't much demand for it. Things like clojure.spec and alike (compile-time + run-time typing) seems much more popular, but isn't static.
To be honest, I'd kill for a Lisp that had the same type system as OCaml, but I suspect the closes we'll get is basically Rust (whose macro system is quite good).
Dead Comment
Notable is the lack of call/cc, but in my "armchair expert" opinion, it's the ugliest part of the language. Yes, continuations as a first-class object are elegant and succinct, but in order to do anything actually useful with them (like implementing exceptions), you need library code, which makes them much less composable.
I think there's a much more pleasant and practical language lurking somewhere between R6RS "big" and traditional "small" Scheme, but I feel it would take a BDFL to flesh it out.
(Meanwhile, back to fixing my init.el.)
I will be watching this closely!
With the Ableton Live Notes API, enabling something similar is one of the things I plan on adding to Scheme for Max this year.
Thanks for the tip about who wrote it, I will look him up!
The freestanding macro suggests most of the heavy lifting is done. Stuff the GPU targets will struggle with in no particular order:
- setjmp / longjmp
- signals (if used?)
- threads
- fast alloc/free
- stack will be smaller than chicken expects
I don't know how to do signals. The rest are merely difficult.
Isn't that mostly needed by call/cc, which is not supported by Crunch?
Also its small size would make it a perfect target to compile to typescript/deno/wasm without rejecting the s-exp power and runtime possibilities in its full chicken code at the backend...
A recent paper (see also the presentation on YouTube):
Leonard Oest O'Leary, Mathis Laroche, and Marc Feeley A R4RS Compliant REPL in 7 KB
For systems with a C compiler:
Vincent St-Amour and Marc Feeley. PICOBIT: A Compact Scheme System for Microcontrollers. (This one got a best paper award).
Finally, there is also PICBIT available for PIC microcontrollers:
PICBIT: A Scheme System for the PIC Microcontroller
You even get a REPL and everything WHILE running on the hardware. Super easy to set up and get going. Though as it is interpreted so you will of course not have native performance. Still very useful for prototyping and hobbyist projects.
Even interpreted on a several hundred MHz classic RISC microcontroller, Lisp will chew through a million cons cells a second or more - an order of magnitude or so faster than the old Lisp machines in the 80s were and they used to run giant CAD systems on those to design aircraft and stuff. (Albeit slowly...)