Add docs on arrays and ranges (#6890)

Signed-off-by: Nick Cameron <nrc@ncameron.org>

docs/kcl-lang/arrays.md

@@ -0,0 +1,32 @@
+---
+title: "Arrays and ranges"
+excerpt: "Documentation of the KCL language for the Zoo Design Studio."
+layout: manual
+---
+
+Arrays are sequences of values.
+
+Arrays can be written out as *array literals* using a sequence of expressions surrounded by square brackets, e.g., `['hello', 'world']` is an array of strings, `[x, x + 1, x + 2]` is an array of numbers (assuming `x` is a number), `[]` is an empty array, and `['hello', 42, true]` is a mixed array.
+
+A value in an array can be accessed by indexing using square brackets where the index is a number, for example, `arr[0]`, `arr[42]`, `arr[i]` (where `arr` is an array and `i` is a (whole) number).
+
+There are some useful functions for working with arrays in the standard library, see [std::array](/docs/kcl-std/modules/std-array) for details.
+
+## Array types
+
+Arrays have their own types: `[T]` where `T` is the type of the elements of the array, for example, `[string]` means an array of `string`s and `[any]` means an array of any values.
+
+Array types can also include length information: `[T; n]` denotes an array of length `n` (where `n` is a number literal) and `[T; 1+]` denotes an array whose length is at least one (i.e., a non-empty array). E.g., `[string; 1+]` and `[number(mm); 3]` are valid array types.
+
+## Ranges
+
+Ranges are a succinct way to create an array of sequential numbers. The syntax is `[start .. end]` where `start` and `end` evaluate to whole numbers (integers). Ranges are inclusive of the start and end. The end must be greater than the start. Examples:
+
+```kcl,norun
+[0..3]      // [0, 1, 2, 3]
+[3..10]     // [3, 4, 5, 6, 7, 8, 9, 10]
+x = 2
+[x..x+1]    // [2, 3]
+```
+
+The units of the start and end numbers must be the same and the result inherits those units. 

docs/kcl-lang/index.md

@@ -14,6 +14,7 @@ things in a more tutorial fashion. See also our documentation of the [standard l
 * [Values and types](/docs/kcl-lang/types)
 * [Numeric types and units](/docs/kcl-lang/numeric)
 * [Functions](/docs/kcl-lang/functions)
+* [Arrays and ranges](/docs/kcl-lang/arrays)
 * [Projects and modules](/docs/kcl-lang/modules)
 * [Attributes](/docs/kcl-lang/attributes)
 * [Importing geometry from other CAD systems](/docs/kcl-lang/foreign-imports)

docs/kcl-lang/types.md

@@ -19,18 +19,6 @@ myBool = false
 
 Currently you cannot redeclare a constant.
 
-## Arrays
-
-An array is defined with `[]` braces. What is inside the brackets can
-be of any type. For example, the following is completely valid:
-
-```
-myArray = ["thing", 2, false]
-```
-
-If you want to get a value from an array you can use the index like so:
-`myArray[0]`.
-
 
 ## Objects