Hi all,

I've been a software developer for about 10 years and I've been curious about FP for half of this time. Eventually, I picked up SML as my language of choice (OCaml is mostly some random line nose for me, and in Haskell/PureScript type classes are so pervasive, they make the language almost impenetrable for beginners).

So my goal has been to:

- lex the source code,
- parse it using parser combinators,
- (do some AST manipulations),
- evaluate it.

This is the repository where I keep my source code, and a README file. The gist of this file is:

- it's not Scheme,
- this is a WIP
- compiler: MLton + MLB basis files
- using SuccessorML as much as possible.

I try to keep the code clean, concerns separated as much as possible, meaningful signatures & structs, clear types).

ALL constructive criticism is very much welcome. I'm not an SML pro :)

Hi all,

I always thought SML looked better than OCaml, and the only reason not to use it was that there were no libraries. But if I make some libraries, maybe it'll catch up. Idk.

I built out a bunch of useful shit here

https://github.com/sjqtentacles?tab=repositories&q=&type=source&language=standard+ml&sort=

over 200 repositories so far! Still working on more.

https://gitlab.com/nemurak_steloj/standardml-gameoflife

[EDIT: Found! https://www.cs.cmu.edu/afs/cs/project/fox-15/release/2.0/ ]

Does anyone here have a copy of FoxNet 2.0 sources from 1996?

Unfortunately, the FTP sites (!) linked from https://www.cs.cmu.edu/~fox/foxnet.html are defunct.

So far, I've managed only to find a potential copy of FoxNet 1.0 from 1994, via https://github.com/briangmilnes/foxtnet .

Does anyone here happen to have a copy of FoxNet 2.0 squirrelled away? It's an interesting and arguably important bit of history, worth preserving IMO, if it hasn't already been lost!

I've uploaded what I've managed to find so far to https://git.leastfixedpoint.com/tonyg/FoxNet -- I'll update it if/when I find more.

The program: ML family workshop

The Session video start

Some interesting talks, in particular the first one by Dave MacQueen about a possible modernized syntax and frontend for SML/NJ.

fun length x =
    if null x then 0
    else 1 + length(tl x);

fun thirdElem L = 
    if length(L) < 3 then 0
    else hd(tl(tl(L)));

I understand that a function takes a value of a certain datatype, and returns a value of a certain datatype, but it gets annoying when I want a function fn: 'a list -> int but the function I coded becomes int list -> int.
For example, the function thirdElem is fn: int list -> int, which means it absolutely cannot work on anything but an int list, like a char list or string list, even though I want it to.

So in order to have it accept more than just an int list, I would need to turn it into fn: 'a list -> something else.
Is there absolutely no way to do this? Because the length example from my book takes 'a list so it will work on an int list, char list, whatever.

It took some time for me to find this (original announcement):

https://www.reddit.com/r/sml/comments/kacoad/join_the_standard_ml_chat_at_standardmlmatrixorg/

Room is here: https://app.element.io/#/room/#standardml:matrix.org

Its slightly better experience than #sml on libera IRC.

I'm trying to figure out the following error message:

main.sml:28.6-32.18 Error: operator and operand do not agree [tycon mismatch]
operator domain: {eResult:TestHarness.Value, input:TestHarness.Value,
                  name:string, test:TestHarness.Value -> TestHarness.Value}
operand:         {eResult:TestHarness.Value, intput:TestHarness.Value,
                  name:string, test:TestHarness.Value -> TestHarness.Value}
in expression:
    TestCase {name=n,intput=inp,eResult=er,test=runFn}

It seems to be telling me that two record types with the same field names and types are different when I'm trying to apply a type constructor. I don't understand why the two records are different.

For some context, here is part of the structure that defines TestCase and TestHarness.Value:

structure TestHarness : sig 
   datatype Value = Int of int | String of string | AST of AST.AST
   (* test case name * input * expected result * fn to test *)
   datatype TestCaseTy =
      TestCase of
      {
         name : string,
         input : Value,
         eResult : Value,   (* expected result *)
         test : Value -> Value
      }
(* other stuff omitted, since it compiles without warning or error *)

And here's the code that's generating the error message:

structure TH = TestHarness;
fun mkTestCase ( n:string, inp:TH.Value, er:TH.Value, runFn:TH.Value -> TH.Value ) = 
  TH.TestCase { name = n,    (* This is line 28 of the error message *)
                intput = inp, 
                eResult = er, 
                test = runFn }

I'm trying to make a record of type TH.TestCase out of a tuple. Why, you might ask? I'm building a compiler in SML and as it gets more complicated I'm trying to add types rather than using tuples for everything.

I'm using Standard ML of New Jersey (64-bit) v110.99.5 [built: Thu Sep 26 15:40:34 2024]

Hi, I want to learn more about functional programming so I thought that the best way would be to reinvent the wheel for the thousandth time just for fun (and for fun only). I have a hobby experience with some more advance topics as well with regards to FP so I'm not a total n00b. Anyway, I'm designing a simple chain of signatures:

FUNCTOR -> APPLICATIVE -> MONAD -> EFFECT (IO)

The signatures (relevant parts) are as follows:

[functor.sig]

signature FUNCTOR =
sig
  type 'a f

  val fmap : ('a -> 'b) -> 'a f -> 'b f
end

[applicative.sig]

signature APPLICATIVE =
sig
  include FUNCTOR

  val pure : 'a -> 'a f

  val apply : ('a -> 'b) f -> 'a f -> 'b f   
end

[monad.sig]

signature MONAD =
sig
  include APPLICATIVE

  val bind : 'a f -> ('a -> 'b f) -> 'b f
end

[effect.sig]

signature PRIM_EFFECT =
sig
  include MONAD

  type 'a effect

  (* ... *)
end

[effect.sml]
structure PrimEffect :> PRIM_EFFECT  =
struct
  datatype 'a effect = Effect of (unit -> 'a)

  type 'a f = 'a effect

  (* ... *)
end

Now, I have a main file:

local
  open Prim.Effect
in
  val eff = (printEff "hello") *> (printnEff "world")

  val _ = runEff eff
end

With opaque ascription structure PrimEffect :> PRIM_EFFECT I'm getting the following error:

incompatible types: PrimEffect.f and PrimEffect.effect are different type constructors
  expected ?a PrimEffect.f * _ PrimEffect.f
     found unit PrimEffect.effect * unit PrimEffect.effect

^ Much more readable diagnostics with Millet than with MLTon btw.

Without opaque ascription it works perfectly but it's been bugging so much now because: why are the type constructors different when the opaque ascription is employed? From what I've gathered, the types may be abstracted using this kind of ascription so it doesn't "leak" and the only way of creating an effect would be through the applicative's pure function. I don't want to expose the Effect constructor.

I've tried to find the answers in "Programming in Standard ML ’97: A Tutorial Introduction" by Gilmore and "Programming in Standard ML" by Harpner but to no avail. I'd be more than glad if someone could guide me through it and tell me how is that wrong. Inb4 no, I'm not gonna use ChatGPT for that.

Related to my previous post, but a somewhat different point: Real.toString implementations differ when outputting whole numbers. For the following function:

fun real2() = print(Real.toString (real 2))

SML/NJ 110.99.7.1 prints 2, MLton prints 2, but PolyML prints 2.0, and SOSML (on the web) prints 2.0. This variation seems problematic. I commented about this a few days ago on Github, regarding issue #330, cited in my previous post. I added that Reppy and Ganser's The Standard ML Basis Library, p. 367, says, I think, that it should be 2, not 2.0. David MacQueen has now commented on this, yesterday, addressing the difficulties involved in an issue like this, but also saying that in this case he favors 2.0. https://github.com/smlnj/legacy/issues/330#issuecomment-2810436727

This seems contrary to what I remember, is confusing, and feels wrong. It also differs from SOSML and tutorialspoint web sml/nj. Does anybody know why this was changed? I am running version 110.99.7.1.

EDIT: It's a bug. See https://github.com/smlnj/legacy/issues/330 .

Slick&Moonro

https://github.com/mnegovanovic/slick-moonro

You will need OpenResty, LunarML and SMLToJS ... check it out.

I tried writing a simple DLL that exports a function like so
fun add(a: int, b: int): int = a + b

val _ = _export "add": (int * int -> int) -> unit;

and then another program that uses it

val add = _import "add": (int * int) -> int;

fun main () =
  let
val result = add(5, 3)
  in
print("5 + 3 = " ^ Int.toString result ^ "\n")
  end

val _ = main()
the resultgiosc@DESKTOP-D2F4QJP MINGW64 /c/Users/giosc/sml/windowsprogramming

mlton -default-ann 'allowFFI true' -format library DllMain.sml

giosc@DESKTOP-D2F4QJP MINGW64 /c/Users/giosc/sml/windowsprogramming

mlton -default-ann 'allowFFI true' -link-opt DllMain.dll -output testimport.exe testimport.sml

giosc@DESKTOP-D2F4QJP MINGW64 /c/Users/giosc/sml/windowsprogramming

./testimport.exe

Segmentation fault

what am I doing wrong?

Is there a 64-bit version of SML/NJ available for Windows? The pre-built binary distribution appears to only be 32-bit and the references for building from source using Cygwin also only mentions 32-bit.

I've been searching the Basis Library!

Is "The ListPair structure" the one to use to get a hash to happen?

Seems a little clumsy, but what do I know - right? :)

Reading "A Gentle Introduction to ML" by Andrew Cumming and doing the exercises.
The current exercise is asking to write a function such that when a string is input, the output is, e.g.
incFirst "bad" = "cad"
incFirst "shin" = "thin"

I came up with a solution that choked on my Linux box running

sml -h
Standard ML of New Jersey v110.79 [built: Tue Aug 8 16:57:33 2017]

So I cheated and looked at the solutions at the end of the book and found this:
fun incFirst s = chr(ord s + 1) ^ substring(s, 1, size s -1);
but it chokes the interpreter as well. Imagine!!

I sure could use some in-a-nutshell type of assistance please. TIA ..