Silent-Lang | Array Design

I want arrays in silent-lang to be as intuitive as possible, this is what happened to my design.

Array creation

let n = input
let initedArray = [0 rep n]
let uninitedArray = [rep n]
let fixedArray = [2, 3, 4]

Uninited array begins with random values, they should be treated as non-accessible.

The rep keyword (stands for “repeat”) is for avoiding ambiguity between value multiplication, while keeping a semantically-clear syntax.

Array indexing

Same as C, just:

let arr = [2, 3, 4]
let _ = print(arr[0])

0 means the first element.

Array modification

let n = input
let arr, x, y = [input rep n], input, input
  upd arr[x <- arr[y], y <- arr[x]], x, y

Please note that an instance of array is affine, meaning that:

• After being referenced as a whole (not indexing), it can no longer be used
• Being referenced is not mandatory

For example, this is illegal:

let n = input
let arr, x, y = [input rep n], input, input
  upd arr[x <- arr[y]][y <- arr[x]], x, y

Reason: after calculating arr[x <- arr[y]], arr is no longer referenceable. Please always remember that let is associating a name with contents of specific memory address, not manipulating memory directly, which is the duty of referencing.

Array length

I would probably use a struct to represent an array:

struct array {
  int length;
  int *ptr;
}

This way, you can refer to the length (capacity) of an array with:

let arr = [1, 2, 3]
let _ = print(len(arr)) // 3

Just like Golang.

Array typing

I’d like to add dependently-typed arrays afterwards, but for now I’ll just make a simple one:

let f = (1 arr: int[]) => arr[0 <- 5]
let _ = print(f([2, 3, 4])[0]) // 5

Just like C.

Not supported

Array concatenation

Concatenation violates the philosophy of silent-lang: view mutations as silent functions from state to state, not how to dynamically construct the result.

Dynamic-lengthed Array

Once finishing structs in silent-lang, dynamic-lengthed array can be implemented inside silent-lang. I want the core language to contain as few features as possible.