Four Lectures on Standard ML (1989) [pdf]
45 comments
·March 30, 2025toolslive
sheepscreek
It’s incredible how much of an understatement it is to say that F# and OCaml were “inspired” by Standard ML. They’re practically step-siblings, sharing more similarities than I could have ever imagined.
Edit: Obviously, F# is the step-sibling here, given its half-dotnet parentage. However, they’re all solid choices. Their spectacular type inference makes coding in them a very gratifying experience. I can only think of TypeScript as the closest to them among the more popular modern languages.
int_19h
For those curious about the differences between Standard ML and OCaml.
moomin
C#’s inference is pretty good these days. As with most things with powerful type inference, you can make a real mess if you put your mind to it.
nextos
The Little Series, famous for The Little Schemer book, published The Little MLer in 1998.
It's probably their lesser known volume, but IMHO it makes a terrific job at teaching the ML family and its features.
ngruhn
it's crazy, it took "the industry" 30+ years to adopt this stuff
fire_lake
And they still haven’t! Although expressions over statements would be a breaking change - I can’t see any mainstream language making this switch.
tialaramex
Barry Revzin has written a paper to try to give C++ expressions like this. It's ugly, even by the standards of C++ but it would work. The rationale is that C++ 29 or C++ 32 wil probably get pattern matching and pattern matching doesn't have great ergonomics if everything is a statement rather than an expression. There are plenty of other things C++ will need to fix once it gets pattern matching, but the direction makes sense if you insist on trying to teach this particular old dog new tricks.
Also, I think Rust would consider itself to be a mainstream language, though they aren't techically "making this switch" because the language has always been expresion oriented from the outset. The Book has about two paragraphs about the statements in the language and then a whole chapter on expressions because almost everything is an expression.
BalinKing
I actually think it's becoming fairly common these days—IIRC Ruby and Rust both prioritize expressions over statements.
tmountain
Still waiting on real pattern matching in TyoeScript.
Almondsetat
do you have any research that points to these things being useful for the industry?
sudahtigabulan
The languages that were actually adopted by the industry are not exactly full of great useful stuff:
rokkamokka
This was the language they taught in our functional programming course while I was doing my CS degree. That was around 15 years ago now. I wonder if they still use it in the course
null
cmrdporcupine
Having SML (or at least OCaml) as a known language definitely would help engineers when they get into the industry and start using Rust.
Back in the day when I played with these things I preferred SML/NJ over OCaml, but OCaml "won" the battle for headspace.
I'd consider using OCaml for new projects, I really like the language family.
xyproto
I also prefer SML over OCaml. I wonder how F# feels and want to give it a shot.
int_19h
F# doesn't have many of OCaml's more advanced features. In particular, no functors and no polymorphic variants. Also the OO system is basically .NET, which isn't that surprising (but means that you don't get the neat row typing with inference that OCaml does).
OTOH some of the choices it makes are a bit more pragmatic - e.g. arithmetic is overloaded for ints and floats, locals can be marked as mutable similar to record fields, and fields are scoped to record types (so different types can use the same field name).
cantrevealname
FYI for everyone: This is not about Machine Learning. It is about a programming language called Standard ML where ML stands for Meta Language[1].
tialaramex
I was taught the Standard ML of New Jersey (which as a non-American I did not realise is a joke, it's referring to the company now known to you as Exxon, the Standard Oil of New Jersey) at university.
I strongly believe that - although my home institution no longer teaches an ML as first language - this is the best way to teach CS to undergraduates. An ML has all the fundamental ideas you will need to also teach about this discipline, and (so long as you choose e.g. SML/NJ or similar, not Rust or something) it won't be a language the average teenager you recruited might already know, so the week 1 exercise showing they've understood what they're doing is actually work for all of your students, averting a scenario where some of them drift away only to realise at exam time that they haven't learned a thing.
sshine
Thank you for sharing this American joke.
Standard ML was my go-to language for many years.
I always found SML/NJ complicated both to compile and use, compared to...
...well, pretty much every other compiler: Moscow ML, Poly/ML, MLton, MLKit.
jjice
Agreed - we wrote an ML style language in my uni compilers course and it was taught by the primary maintainer of MLTon (Dr Fluet is a great guy). Since it’s full program optimizing, the compilation took a while. He told us to give SML NJ a try for faster compilation but slower execution. It was a headache and only marginally faster compilation for our use case.
That said, it’s the OG so I give it some slack. I did enjoy MLton though, but it’s easier to do when the instructor wrote it.
layer8
> Exxon, the Standard Oil of New Jersey
It would have been fun if they had renamed to JSON instead of Exxon.
smlismyhomeboy
Huh. As an American, I had just assumed it was because it was developed at Princeton.
JoelMcCracken
Ditto! I've never heard of "Standard Oil of New Jersey" myself.
pkal
Not everyone; I'm the kind of person who wishes posts about machine learning would be prefixed with these kinds of clarifications ("watch out, this is not related to the programming language but a family of stochastic algorithms referred to as 'machine learning'"), because I consistently fall for it.
belter
"Generational list of programming languages" - https://en.wikipedia.org/wiki/Generational_list_of_programmi...
msarnoff
My favorite bit of SML trivia: the infix function composition operator is “o” — lowercase letter o — so you can write ‘(f o g)(x)’ just like mathematical notation.
ckmate-king-2
Note that these lectures are from 1989, but the definition of Standard ML was revised in 1997. See, e.g., https://www.smlnj.org/sml97.html.
swatson741
Defiantly worth studying SML imo. Pattern matching is a cool feature. Although it's not as comprehensive as most of the pattern matchers in Lisp. You can't match on bitfields, comparisons other than equality by value, etc.
Datatypes are just ok. Classes would be better. It's sort of strange to represent lists (and everything else) as enumerations. It's not really essential or fundamental but I guess that's what Lisp is for.
ossopite
I suppose by enumerations you mean sum types. I would argue that these are pretty fundamental? you have product types (structs/records/tuples) - a value is made up of x and y - and sum types - a value can be either X or Y. I think the combination of these is what you need to precisely express any concrete data type.
swatson741
I did mean sum types, variants, etc. It's not really clear what I meant by representing the data but I'm referring to type inference. SML can't solve the problem, and Lisp doesn't have it.
uzername
We used SML in my undergrad compilers course. I really loved the language and I started exploring other languages outside of class after that.
trollied
My CS degree course used SML as the first language to teach everyone in the first semester. Put everyone on the same level, as it was unlikely people would have prior experience. Also made it easy to teach things like recursion.
Really enjoyed it.
peterstjohn
Ha, same here! It really helped my imposter syndrome, as I overheard a couple of guys talking about the ARM assembly they were doing on their Archimedes on the first day…and I hadn't written anything fancier than QuickBASIC at the time…
trollied
Was actually lucky enough to be taught by the co-inventor of the ARM cpu. Furber is awesome.
peterstjohn
For my sins, I didn't actually realise how great that was until quite a bit afterwards! ;)
Studying SML should be part of the entry examination for programming language designers. It's old, has its warts, but is still vastly superior to most things that came later. (Type inference? check! Pattern matching? check! TCO? check!. Performance ? excellent!, ...)