Amber gives us the ability to generate an array of numbers [Num] of certain range. There are two types of ranges:

• a..b is exclusive from a to b excluding b.
• a..=b is inclusive from a to b including b.

echo 0..10
// Outputs: 0 1 2 3 4 5 6 7 8 9
echo 0..=10
// Outputs: 0 1 2 3 4 5 6 7 8 9 10

We learned about array literals in the first chapter. In this chapter we will learn how to make use of them. Arrays are indexed from zero.

To store or retrieve a value at a particular index of an array, we can use the following syntax:

let groceries = ["apple", "banana", "cherry", "date"]
groceries[0] = "kiwi"
echo groceries[1]
// Outputs: banana

As of right now (Amber alpha) the subscript syntax does not work with expressions. This means that we can't evaluate expressions like foo()[0] yet.

We can also echo an entire array:

echo groceries
// Outputs: kiwi banana cherry date

To retrieve a slice between a pair of indices of an array, we can use an exclusive range a..b or inclusive range a..=b (see above) with the following syntax:

echo groceries[1..3]
// Outputs: banana cherry
echo groceries[1..=2]
// Outputs: banana cherry

It is not currently possible to replace a slice of an array. This means that we can't evaluate expressions like groceries[1..=2] = ["kiwi"] yet.

To add an element to an array, we can use the mentioned in the expressions chapter addition operator to merge two arrays together.

let capitals = ["London", "Paris"]
capitals += ["Warsaw"]
let cities = capitals + ["Barcelona", "Florence"]

In order to see more operations on the array data type take a look at the standard library documentation which covers functions such as join, len or sum.

We already learned that Bash does not support nesting arrays. But what makes this limitation? The answer is that under the hood Bash defines arrays that essentially only store structures containing string value. You can learn more about Bash arrays by reading the official source code.

typedef struct array {
    arrayind_t max_index;
    arrayind_t num_elements;
#ifdef ALT_ARRAY_IMPLEMENTATION
    arrayind_t first_index;
    arrayind_t alloc_size;
    struct array_element **elements;
#else
    struct array_element *head;
    struct array_element *lastref;
#endif
} ARRAY;

typedef struct array_element {
    arrayind_t ind;
    char *value;
#ifndef ALT_ARRAY_IMPLEMENTATION
    struct array_element *next, *prev;
#endif
} ARRAY_ELEMENT;