What is FN in SML?
If you type the square_root declaration above into the SML top-level, it responds with: val square_root : fn real -> real. indicating that you’ve declared a variable (square_root), that its value is a function (fn), and that its type is a function from reals to reals.
What are constructors in SML?
It is important in SML to distinguish constructors from ordinary functions. Constructors are the primitive functions that create new values of a data. For example, the constructors for lists are :: and nil . The append function @ is not a constructor (it can be defined using :: and nil ).
How do you test SML?
To test ML functions, go to the sml window. Enter the command use “filename. sml”; to load and compile the file you’ve just edited. You can interactively test each function as you add it.
How do you negate in SML?
Note that negative numbers in SML are written using ~, as in ~1, ~3 etc.
How do I write a character in SML?
For example, #”\^A” is equivalent to #”\001″ . The SML system presumably uses its own Char. toString function to print values of type char . Try chr 65 , which should be printed as #”A” .
How do I run SML?
Click on the Start button, and choose the Programs menu. From there, select the Server Apps menu, and finally select SML NJ 109.28. To use the SML interpreter as you would from a shell, choose the run sml-cm option.
How do I write a character in sml?
What is sml error?
This error message indicates how the parser attempted to “repair” the input (from a file foo. sml), and in this case indicates that the parser thinks that val is needed after the let (at line 1, column 5 of foo. sml).
How do I use SML REPL?
Using the SML/NJ REPL (Read-Eval-Print Loop) in Emacs
- Edit a file with extension .
- To open the SML/NJ REPL within Emacs, type C-c C-s (and then Enter to accept the sml interpreter) while working in an SML-mode buffer.
- To end a REPL session, type C-d while the cursor is at the REPL prompt in the *sml* buffer.
How do you determine the type of variable in SML?
Show activity on this post. Then you can pattern-match on the constructor: case x of Int x -> foo | Real x -> bar | String x -> In this case, x is clearly typed as a wrapper , so that will work.
How do I save a SML code?
Save code in simple text files with a . sml extension (if you are on a Windows machine — the editor Textpad is fairly nice: https://www.textpad.com/ . You can download an SML syntax definition file for syntax highlighting). Then, in the REPL, type use “path/filename.
How do I use SML in NJ?
Once in the SML mode, you can start SML/NJ by typing M-x sml, or by selecting SML/Process/Start default ML compiler from the menu. This will start SML/NJ running in the background. You can then bring up an SML/NJ window by typing C-c C-s, or by selecting SML/Process/switch to ML buffer from the menu.
How do I save an SML file?
What is SML cons?
The other essential component to lists is what is known as the :: operator, referred to as “cons”. Cons can be used as a constructor for any fixed type of list, so we say that for any given type t : (op ::) : t * t list -> t list.
How do I find the length of a list in SML?
Here is a pattern-matching straight recursion version which doesn’t use the built-in length function but instead computes the total length (“tol”) directly: fun tol [] = 0 | tol ([]::xss) = tol xss | tol ((x::xs)::xss) = 1 + tol (xs::xss);
What is SML language?
Standard ML (SML) is a general-purpose modular functional programming language with compile-time type checking and type inference. It is popular among compiler writers and programming language researchers, as well as in the development of theorem provers.
How do I use SML files?
The simplest way to load files in the SML/NJ interactive system (at the “-” prompt that you get when you run sml), is to call the use function, passing it the file name or path as a string. So to load two files we can call use twice, passing the appropriate file names. – use “wff-mod. sml”; – use “pc.
Why are lists homogeneous in SML?
Lists in SML are therefore homogeneous lists, as opposed to heterogeneous lists in which each element can have a different type. Lists are immutable: you cannot change the elements of a list, unlike an array in Java.
How does map work in SML?
map. The map function takes a function F and a list [a1,a2,…,an], and produces the list [F(a1), F(a2),…, F(an)]. That is, it applies F to each element of the list and returns the list of resulting values.