What is the meaning of '[..]'?

[bentxt]

Hi all

I just read this declaration in a library file

operator [..] --from=0 --to=size -> string:
What is the meaning of '[..]'?

Its a bit hard to search for.

Thanks
Ben

[floitsch]

It the "slice" operator of Toit.

When the compiler sees o[x..y] (where both x and y can be omitted), then that expression resolves to the operator [..] --from=x --to=y.

It is used in strings and lists to get subsections of them:

main:
  str := "1234"
  sub := str[1..]  // => "234"
  sub = str[2..3]  // => "3"

  list := [1, 2, 3, 4]
  sub_list := list[..2]  // => [1, 2, 3]

Note that slices are generally implemented as views into the object. This means that a slice of a big string might keep the string alive.
Similarly, a slice of a list is a view into the list. Changing one, affects the other.