作用域与可见性

val: 42
A: {
	val: 23
	num: val // will be 23, matches locally

	// irregular names need to be quoted and require indexing to access
	"user-id": "abc"
	UserID:    A["user-id"]
}
A: {
	b: val   // 42, matches top-level
	c: A.num // 23, reference A.num

	// num itself is not in scope even though it is part of A
}

import "strings"

label: "app"
// alias for label
let L = label
S: {
	name: "Postgres"
	// intermediate value
	let lower = strings.ToLower(name)
	version: "13"
	label:   L
	image:   "docker.io/\(lower):\(version)"
}

A: {
	a:    "A"
	"2f": 3
	l: ["cow", "moo"]
}

a: {
	// either is valid
	f1: A.a
	f2: A["a"]
	// must index
	f3: A["2f"]
	// list index
	f4: A.l[1]
}

// a mathematically valid releationship
// but invalid in Cue until one or the other has a value
a: b - 10
b: a + 10

// we need to set a or b and Cue will do the rest
// if not, a cycle error will be reported
a: 100

#List: {
	val:  _
	next: #List | *null
}

// Cannot do this, it is structural recursion
#Contains: {
	list:  #List
	val:   _
	found: bool | *false

	if list.val == val {
		found: true
	}
	if list.val != val && list.next != null {
		// No recursion!
		found: #Contains & {"list": list.next, "val": val}
	}
}

// We can define an infinite structure
list: #List & {val: "a", next: {val: "b"}}

// results in
list: {
	val: "a"
	next: {
		val:  "b"
		next: null
	}
}