sml

I need to create a new instance of a lexer tied to the standard input stream. However, when I type in val lexer = makeLexer( fn n => inputLine( stdIn ) ); I get an error that I don't understand: stdIn:1.5-11.13 Error: operator and operand don't agree [tycon mismatch] operator domain: int -> string operand: int -> string option in expression: ( makeLexer is a function name present in my source code) inputLine returns a string option , and my guess is a string is expected. What you want to do is either have makeLexer take a string option , like so: fun makeLexer NONE = <whatever you want to do

Is there a Java BigInt equivalent for Standard ML? The normal int type throws an exception when it overflows. Yes, see the IntInf structure. The official SML'97 standard basis library introduces a zoo of structures like Int, IntInf, Int32, Int64, LargeInt etc. To actually use them in practice to make things work as expected, and make them work efficiently, you need to look closely at the SML implementation at hand. One family of implementations imitates the memory layout of C and Java, so Int32 will be really a 32bit machine word (but with overflow checking), and Int64 a 64bit machine word.

In SML, the following is possible for modelling lazy programming, // Have a datatype to wrap a computation datatype 'a susp = Susp of (unit -> 'a) // A function to hold the computation fun delay(f ) = Susp(f) I know that closures can be written using Blocks , int multiplier = 7; int (^myBlock)(int) = ^(int num) { return num * multiplier; }; So I think I can use it as a function argument. The next step would be how to use functions with no real arguments ( unit value e.g. in SML fn () => ) and creating lazy datatypes as the one above. Is this possible or should I be pursuing a different more

I know that semicolons are used as terminators in REPL. But I'm confused about when to use them in a source file. For example it is not necessary after val x = 1 . But if I omit it after use "foo.sml" , the compiler will complain about it. Then, what are the rules on using semicolons? Semicolons are used for a number of syntactic entities in SML. They are normally used to create sequences of, e.g., expressions or declarations. Here's a link to the SML grammar: http://www.mpi-sws.org/~rossberg/sml.html In your case, you are interested in the semicolon for declarations (the dec class). Note that

I need to construct an undirected graph. I don't need it to do anything too fancy, but ideally it would work like this: structure UDG = UndirectedGraph val g = UDG.empty val g = UDG.addEdges(g, n1, [n2, n4, n7]) (* n1 is connected to n2, n4, and n7 *) val g = UDG.addEdge(g, n2, n3) UDG.connected(g, n2) (* returns [n1, n3] *) Is there a good data structure in SML/NJ to model these relationships? Should I just roll my own? Updates I've gone ahead and tried rolling my own, but I get a type mismatch error when I try to test it. My experience with SML structures and functors is pretty basic, so I