In smlnj, how do you convert "string option" to "string"?

Question

Please help, I do not know how the line does this.

Is it possible to convert a string to a string?

+3

Fred Jun 07 '11 at 16:46

3 answers

insumity · Answer 1 · 2011-06-08T14:39:04+0000

As already stated, you can use pattern matching to get the desired result. So something like this:

fun foo(NONE) = ""
  | foo(SOME a) = a;

But you could save and use Option.valOfthe SML function instead:

Option.valOf(SOME "my string");(Or just valOf(SOME "my string");as pointed out in the comments of newacct).

Andrew · Answer 2 · 2011-06-07T17:42:47+0000

"option" ML - , , Nullable .NET. None Some of 'a ( 'a option). , 'a, .

, None, . , , None, , .

Bernd · Answer 3 · 2011-07-14T16:23:08+0000

:

val x = "String";

(* , : *)

val stringfromoptionstring = case x of SOME s = > s | NONE = > "No String found";