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Array Constants or Initialization

Creating Pre-initialized Arrays in other languages:

C, C++, Java, C#:

int a[] = {1, 2, 3, 4};

Rust

let a = [1i32, 2i32, 3i32, 4i32];

Scala

val a = Array(1, 2, 3, 4)

Go

a := []int{1, 2, 3, 4}

Swift

let a = [1, 2, 3, 4]

Perl

@a = (1, 2, 3, 4);

Lua

a = { 1, 2, 3, 4 }

Python, Ruby, Groovy, node.js

a = [1, 2, 3, 4]

Haskell / Prolog / Erlang / Elixir

[1, 2, 3, 4]

F#

[1; 2; 3; 4]

Ada

A: array(1..4) of Integer := (1, 2, 3, 4);

Fuzions Approach to Pre-initialized arrays

Pre-initialized Arrays

Basic ideas:

  • brackets [ ] seem most popular and go well with using brackets to access an element as in a[i].
  • Requiring a type identifier is awkward.
  • The type should be inferred from the array elements.
  • If array is assigned to a field, that field's type can be used to infer the type instead.
  • The resulting arrays should be immutable, persistent arrays
  • In case elements are mutable, we need new instances of the arrays for every use.

So, in Fuzion, we would have:

a := [1, 2, 3, 4]               # array of default integer type (i32 or i64, need to decide)

b array u16 := [1, 2, 3, 4]     # array of u16, inferred from field b

write(bytes array u8) is ...
write [1, 2, 3, 4]              # array of u8 inferred from field write.bytes

ix := 2
c := [1, 2, 3, 4][ix]           # array of default integer type (i32 or i64, need to decide)

ix := 2
d i64 := [1, 2, 3, 4][ix]       # array of default integer type, 3 will be converted to i64

e i16 := [1, 2, 3, 4][ix]       # array of default integer type, error since not assignable to i16

f := [1, true, "abc"]           # array of Object, boxed elements

g := [1, true, 3]               # array of Object, boxed elements

h array (i32 | bool) := [1, true, 3]
                                # array of i32 | bool, no boxing but tagged choice values

Pre-initialized Lists

Lists (unions of nil and a Cons A (list A) cell) also need syntactic sugar for initialization. Since array is convertible to list via array.asList, it would be convenient to just stick with the same syntax for pre-initialized lists:

l := [1, 2, 3, 4].asList        # list of default integer type (i32 or i64, need to decide)

m list i32 := [1, 2, 3, 4]      # list of i32, implicit call to asList

The type inference for initialized arrays should work for lists as well:

write_list(bytes list u8) is ...
write_list [1, 2, 3, 4]         # list of u8 inferred from field write_list.bytes

f list Object := [1, true, "abc"]
                                # list of Object, boxed elements

g := [1, true, 3].asList        # list of Object, boxed elements

h list (i32 | bool) := [1, true, 3]
                                # list of i32 | bool, no boxing but tagged choice values