Trying to figure out how to get a function that takes a list and returns a list of lists such that the function returns a list of all the permutations of the input list using only recursion and I can't use map or currying.

Example: perms([0,1,2])= [[0, 1, 2], [0, 2, 1], [1, 0, 2], [1, 2, 0], [2, 0, 1], [2, 1, 0]].

Any help would be appreciated.

Here is what I have so far.

fun contains(x, []) = false |contains(x,y::rest) = if x = y then true else contains(x, rest);

fun hce([][]) = false |hce(x::xs,y) = if contains(x,y) then true else false;

What I have so far returns true false true etc for each 1 and non 1 as a list. I need to return only true or only false.

fun isOne(n) =n = 1;

fun containsOne([]) = [] | containsOne(x::rest)=isOne(x)::containsOne(rest);

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.

Here is what I have so far:

fun contains(x, []) = false |contains(x,y::rest) = if x = y then true else contains(x, rest);

fun removeFirst(y, []) = [] |removeFirst(y,x::rest) = if contains(y, x::rest) then removeFirst(y,rest) else x::removeFirst(y,rest);

Hit me up if you're willing to help

fun contains(x, []) = false |contains(x,y::rest)=if x=y then true else contains(x, rest);

take in 2 lists. return a list of what they have in common.

I followed the instructions on the sml/nj site http://smlnj.org/install/index.html but I run into the issue that it asks me to install the 32bit library which I also tried to install libgcc-multilib from rpmseek. The problem is that my system is slinging me a conflict with another package. Here's what I get:

warning: libgcc-multilib-4.7.1-8.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID e4f1bc2d: NOKEY
file /lib/libgcc_s.so.1 from install of libgcc-multilib-6:4.7.1-8.x86_64 conflicts with file from package libgcc-4.9.2-1.fc21.i686

Thank you for the help in advance

I'm doing a homework assignment where this pops up:

type 'a cont  = 'a SMLofNJ.Cont.cont
type choice   = int cont * (int -> int) * int

and I'm confused as to what (int -> int) means. I've seen it before in programs but never in the equation of one. Any explanation would be really appreciated. Also, I'm assuming the 'a cont is an import. If you have any idea what is being imported I'd like to know. Thanks.

Hi guys, did anyone compare sml (smlnj, mlton) performance vs haskell (ghc) ?

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.

Dreyer, Harper, Chakravarty, and Keller's POPL'07 paper describes a very elegant system for type classes (and therefore overloading) on top of Standard ML. It is defined as an elaboration: it takes a program in SML+Classes and outputs a program in ordinary SML.

Was this translation ever implemented anywhere?

Ideally I'm hoping for a standalone translation, but I might switch SML compilers if the only implementation is compiler-specific.

I know there is SML mode for Emacs but since I use Vim, I do not really want to use Emacs.. also I do not want to go into configuring Emacs just for writing SML.

There is a plugin for Vim `vim-better-sml` but I do not particularly like it.. there is no linter and the auto-indentation also feels clunky. It also only supports an embedded REPL with Vimux or Neovim, neither of which I use.

I feel most comfortable with VS Code or Jetbrains IDEs...

Are there any IDEs you could recommend for SML?

I'm trying to implement some algorithms with memoization. Some can be done with arrays, but some need the keys to be strings or integers without regular patterns.

How is this done in SML? SML/NJ has a hash table implementation, but is implementing the associative array ourselves the only pure SML option?

Take leetcode problem 1 as example. The optimization uses an associative array (python's dictionary in this example).

def two_sum(nums: List[int], target: int) -> List[int]:
        hashmap = {}
        for i in range(len(nums)):
            complement = target - nums[i]
            if complement in hashmap:
                return [i, hashmap[complement]]
            hashmap[nums[i]] = i

How can something like this be achieved with pure SML? Should this optimization be approached in another way?