Poly/ML

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5 participants
707 discussions

Type error in function application
by Duke Normandin 21 Jan '26

21 Jan '26

This function: fun divide (x: real, y: real) = if y = 0.0 then raise DivByZero 5 else x / y; is taken from: "Beginner's Guide to Standard ML" It's part of a "calculator" program included in the document. I'm using: $ poly --use ./calc.sml Poly/ML 5.9.2 Release and it chokes and quits at line 4 on the above function. I made no typo! So! What now? Why doesn't Poly/ML not like that code? TIA ... -- Duke

3 4

First step woes
by Duke Normandin 18 Jan '26

18 Jan '26

From: INTRODUCTION TO POLY D.C.J. Matthews,May 1982 Computer Laboratory, University of Cambridge [quote] > begin # print("Hello"); # print(" again") # end; Hello again [/quote] but I get: [quote] > begin # print("hello"); poly: : error: Value or constructor (begin) has not been declared Found near begin print ("hello") Static Errors > [/quote] if I remove the semi-colon, it lets me enter the rest of the code, but chokes after I enter `end;'. Has the syntax changed since the book was written, or am I doing something wrong? TIA ... -- Duke

3 3

Defining a function
by Duke Normandin 18 Jan '26

18 Jan '26

Noob to SML & PolyML here! Trying to solve "exercism" SML track. Lesson2 wants me to create a function as: fun leapyear blah blah I have a bunch of pdf docs for sml-nj, poly/ml etc and none show that syntax to create a function. What am I missing? TIA ... -- Duke

2 3

ML Basis
by vqn 31 Oct '25

31 Oct '25

Hello, Over the past few months, I have been working on an implementation of the ML Basis system for Poly/ML. It supports the complete mlb spec and is available both as a library and a cli tool: https://github.com/vqns/polymlb On a side note, I have been trying to implement incremental compilation by caching compiled .mlb files (i.e compiler namespaces) and exporting and reimporting them through {save,load}ModuleBasic. I have however been running into the issue that exporting each .mlb to a different on-disk module causes opaque types mismatch when reimporting them. What would be the reason for that? I have managed to work around it by exporting everything to the same file, but that result in a fairly large cache, e.g ~45mb for smlfmt (1.2mb executable, 15k loc). I suppose the reason for that is that I export the basis library as well, but I'm not sure there is a solution for that.

3 27

tuple indexing: 0-based or 1-based?
by Gabriel Scherer 28 Oct '25

28 Oct '25

Dear SML people, There is an OCaml feature proposal by Alistair O'Brien that would finally introduce tuple indexing in OCaml -- we currently have only whole-tuple pattern matching: RFC: https://github.com/johnyob/ocaml-RFCs/blob/tuple-projections/rfcs/tuple_pro… discussion: https://github.com/ocaml/RFCs/pull/57 Of course this raises the Very Important Question of whether indexing should be 0-based or 1-based. The argument in favor of 0-based is that it is what we use for arrays, so more consistent, standard in most programming languages. The argument in favor of 1-based is that it is arguably more intuitive (but the inconsistency with arrays weakens this claim noticeably), and that SML uses it. Question: you have a lot more experience using tuple indexing. In your opinion, if this was to be decided again for a new system (no backward-compatibility concerns), would you still recommend using 1-based indices, or would you be more in favor of 0-based indices? P.S.: You may be amused to learn that OCaml recently introduced "labeled tuples" (looking like `(x:1, y:2)` in expressions and `(x:int * y:int)` in types), which are basically a restricted version of SML structural records -- type inference does not try very hard and requires an annotation in practice. P.P.S: Is there still a mailing-list for the SML/NJ crowd? All I could find were github discussions (https://github.com/orgs/smlnj/discussions) and an invite-only Zulip.

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Reusing PolyML's runtime system
by bloop36＠protonmail.com 26 Sep '25

26 Sep '25

Hello everyone, I have just created an ML compiler to experiment with some ideas. The compiler is missing native compilation and a proper REPL, so I'm thinking of reusing the existing backend and runtime system of PolyML to build a complete compiler system. I believe the design of PolyML is modular enough for new frontends to be attached to the existing backend, but I have no idea where to start. Could someone point me in the right direction please? Shuhan HE

2 1

InterruptState
by Rob Arthan 18 Aug '25

18 Aug '25

I realised that I was completely misunderstanding the use of the term “synchronous” in the description of the type InterruptState. I now believe that synchronous interrupts require co-operation from the thread being interrupted while asynchronous interrupts are pre-emptive (not the other way round). Have I got it right now? The documentation says that asynchronous interrupts occur "at a suitable point soon after they are triggered”. Is iit possible to state what the suitable points are. In any case, I think that my code (which is just trying to make a a call of a single-threaded function time out) should loop after sending the sending the interrupt waiting for the interrupted thread to become inactive. Does that sound right? Regards, Rob.

3 3

PolyDoc
by David Matthews 16 Aug '25

16 Aug '25

The recent query about documentation for the HashArray structure reminded me that a while ago I wrote a tool to enable an ML source file to contain documentation. The tool is based on Poly/ML's parser and parses the file, writing signature information to an XML file. The documentation itself is written as specially formatted comments. I've used it to produce the documentation for the Poly/ML-specific modules in the basis library which aren't otherwise documented. The easiest way to understand it is probably to look at the source code for a module such as the Thread structure (e.g. https://github.com/polyml/polyml/blob/master/basis/Thread.sml ) and the output at https://polyml.org/documentation/Reference/Thread.xml . The code is at https://github.com/polyml/polydoc . It may be useful for other projects and I'm open to suggestions for improvement. David

1 0

HashArray structure
by P Padil 12 Aug '25

12 Aug '25

Is there additional documentation of the subject structure? I couldn’d find any in the site. Thanks

2 2

Poly/ML 5.9.2 release
by David Matthews 11 Aug '25

11 Aug '25

Version 5.9.2 of Poly/ML has now been released on GitHub. It has been almost two years since 5.9.1 was released and there have been a few bug fixes since then. Probably the biggest change has been with the conversion from floating point to strings and digit sequences. The old Gay code has been replaced by the Ryu algorithm coded in ML. There have been a few fixes specific to Mac OS. In particular the object code exporter has been changed to deal with a problem with the Xtools 15. There are a number of pull requests outstanding so it's likely that the next release will include some bigger changes. David

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