Standard ML of New Jersey (SML/NJ)
SML/NJ is a popular implementation of the Standard ML programming language that was co-developed jointly by Bell Laboratories and Princeton University. It is released under a BSD like license.
References:
Questions tagged [smlnj]
866 questions
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curried function which takes a function and a list of tuples as input
i am trying to define a curried function which takes a function and a list of tuples as input and returns a Boolean value
for example
values(fn (x,y:int)=>(x-y) [(5,0)];
val it = true:bool
but my problem is i don't know how to pass a dynamic…
Asav Patel
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Returning the position in a list (ML)
Define a function which, given a list L, an object x, and a positive
integer k, returns the position of the k-th occurrence of x in L if x
appears at least k times in L otherwise 0. For example, if L is
[#"a", #"b", #"c", #"b"], x is #"b",…
user2793862
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3 answers
Finding largest value using tail recursion
I'm trying to find the largest value of a list using tail recursion. I can't use any auxiliary functions, though...so it must be done using recursion. I've written a function to find the max, starting from the head, but don't know how to implement…
user2793862
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1 answer
Check whether number is Fibonacci or not in Standard ML
I am trying to write a code which checks if number is Fibonacci or not in ML. I am a beginner. Help me find out what is the problem with my code.
fun isfib(n :int): bool=
let
val a1=1;
val a2=1;
val temp=0;
in
while a2
Asav Patel
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2 answers
New to SML / NJ. Making a custom insert function
Define a function that, given a list L, an object x, and a positive
integer k, returns a copy of L with x inserted at the k-th position.
For example, if L is [a1, a2, a3] and k=2, then [a1, x, a2, a3] is
returned. If the length of L is less…
user2777383
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1 answer
SML - Base case, wrong return value for declared datatype
I'm having trouble with the base case of a function that I'm writing. I have a datatype that I've declared. In the base case I need to replace the nil with something. How do I tell it that the function won't return anything?
datatype 'a newThing…
Andrew_CS
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2 answers
SML - Incrementing a value in a tuple during foldl that needs to be returned
I'm having a problem while trying to increment my value of x inside the inner foldl call. I make x equal to shiftValue that's passed in and attempt to increment it whenever I find a #" " or #"*" in the inner foldl call, but the value of x that gets…
Andrew_CS
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ML compile error in a function
After hours of fixing the following code I got stuck in the following compile error message and no matter what I try, I cannot fix it.
Error: syntax error: deleting END RPAREN FUN
the code is:
fun we (array1 , k, n, fif1) = if Queue.isEmpty fif1…
brera
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SML: Scan a relation list to get all the transitive associations
I have an environment list which keeps associations between variables and values, such as env = [("x", 1), ("y", 2), ("z", 3), ...]. I also have another substitution list (which is returned by a pattern matching control function) that keeps…
Dree
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1 answer
Why can't I access my structure's internal ORD_SET structure?
This exercise I made up is intended to help me understand signatures, structures, and functors in Standard ML. I can't seem to get it to work. Just for reference, I'm using
Standard ML of New Jersey v110.75 [built: Sun Jan 20 21:55:21 2013]
I have…
JeremyKun
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Issue matching Type of function to one defined in signature
I have a structure to define lazily evaluated sequences which are defined as
datatype 'a seq = Cons of 'a option * (unit -> 'a seq)
and I have a function map() that maps a function of type ('a->'b) to the values in the sequence.
val map : ('a ->…
jasimp
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1 answer
How can I convert my data type?
I define a data type for a multi list:
datatype intnest= INT of int
| LIST of intnest list;
now I'm trying to write function which can convert this type to main type.
for example:
[INT 1, INT 2, LIST[INT 6, INT 8]] => [1,2,…
sarah
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1 answer
How can I define a heteregeneous list datatype?
I am just starting to learn SML and having issues. I want to define a datatype, for a list that is not homogeneous.
Take for example
val a = [1,[2,4,3],5,[2,6]]
I have made this datatype
datatype 'a MulList = List of 'a multiList list
…
sarah
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1 answer
inserting EQUALOP error in SML
I am trying to swap elements in a list in ML. My swap function returns the error inserting EQUALOP.
fun swap(n:int, i:int, deck:card list) =
local
val card1_removed = nth(deck,i)
val…
David Farthing
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2 answers
SML/NJ - about ":=" operator
I did some checks on := operator and I want to make sure that I got it well .
let -
val r1 = ref 1 ; (* !r1 = 1 *)
val r2 = ref 2 ; (* !r2 = 2 *)
val r3 = ref 3 ; (* !r3 = 3 *)
r1 := !r2 ; (* !r1 = 2 *)
r2 := !r3 ; (* !r2 = 3 *)
!r1 ; (*…
URL87
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