AppleScript: The Definitive Guide

Containment Operators

Containment may apply to two strings, two lists, or two records. The result is a boolean. Containment implies comparison, and the nature of comparisons involving strings can be influenced by a considering clause; see Chapter 12.

The fact that in the case of list containment both operands must be lists is a little counterintuitive at first. Thus:

{1, 2} contains {2} -- true

You might have expected to say:

{1, 2} contains 2 -- true

You can say that, but only because 2 is coerced to {2} implicitly. In other words, the second operand is not an element; it’s a sublist. Thus you can ask about more than one element at once. For example:

{1, 2, 3} contains {2, 3} -- true

Lists are ordered, so the items of the sublist you ask about must appear consecutively and in the same order in the target list; these are false:

{1, 2, 3} contains {1, 3} -- false
{1, 2, 3} contains {3, 2} -- false

Since lists can contain lists, you may have to use an explicit extra level to say what you mean:

{{1}, {2}} contains {2} -- false
{{1}, {2}} contains {{2}} -- true

The first is false because 2 is not an element of the first list, and {2} is not going to be coerced to {{2}} for you—it’s a list already so there’s nothing to coerce.

In the case of record containment, both the label and the value must match for containment to be true. So:

{name:"Matt", age:"49"} contains {name:"Matt"} -- true
{name:"Matt", age:"49"} contains {title:"Matt"} -- false {name:"Matt", age:"49"} contains {name:"Socrates"} ...