Values in Standard ML

Standard ML (SML) has various value types including strings, integers, floats, booleans, etc. Here are a few basic examples.

(* Strings, which can be concatenated with ^ *)
val _ = print("sml" ^ "lang\n")

(* Integers and floats *)
val _ = print("1+1 = " ^ Int.toString(1 + 1) ^ "\n")
val _ = print("7.0/3.0 = " ^ Real.toString(7.0 / 3.0) ^ "\n")

(* Booleans, with boolean operators as you'd expect *)
val _ = print(Bool.toString(true andalso false) ^ "\n")
val _ = print(Bool.toString(true orelse false) ^ "\n")
val _ = print(Bool.toString(not true) ^ "\n")

To run this program, save it in a file (e.g., values.sml) and use an SML interpreter or compiler. For example, if you’re using the Standard ML of New Jersey (SML/NJ) system:

$ sml values.sml
smlang
1+1 = 2
7.0/3.0 = 2.33333333333
false
true
false

In this Standard ML code:

1. We use ^ for string concatenation.
2. We use Int.toString and Real.toString to convert numbers to strings for printing.
3. Boolean operators in SML are andalso, orelse, and not.
4. We use val _ = ... to execute expressions for their side effects (printing) without binding the result to a name.
5. SML uses (* ... *) for comments.

Note that SML is a functional language, so this example doesn’t follow the imperative style of the original code. Instead, it demonstrates equivalent operations using SML’s syntax and standard library functions.