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are self-contained blocks of functionality that can be passed
around and used in your code.

• Closures

• Security

can capture and store references to any constants and
variables from the context in which they are defined.

• Closures

• Experiments

Global functions are closures that have a name and do not capture any values.

• TRUE

• FALSE

Nested functions are closures that have a name and can capture values from their enclosing
function.

• TRUE

• FALSE

Closure expressions are unnamed closures written in a lightweight syntax that can capture
values from their surrounding context.

• TRUE

• FALSE

as introduced in Nested Functions, are a convenient
means of naming and defining self-contained blocks of code as part of a
larger function.

• CLOSURE EXPRESSIONS

• CLOSURE OPTIMIZATION

are a way to write inline closures in a brief, focused
syntax. Closure expressions provide several syntax optimizations for writing
closures in a shortened form without loss of clarity or intent. The closure
expression examples below illustrate these optimizations by refining a single
example of the sorted(by:) method over several iterations, each of which
expresses the same functionality in a more succinct way.

• CLOSURE EXPRESSION

• CLOSURE OPTIMIZATION

• Inferring parameter and return value types from context
• Implicit returns from single-expression closures
• Shorthand argument names
• Trailing closure syntax

• CLOSURE OPTIMIZATION

• CLOSURE EXPRESSION

When you use the trailing closure syntax, you don’t write the argument label
for the first closure as part of the function call. A function call can include
multiple trailing closures; however, the first few examples below use a single
trailing closure.

• TRAILING CLOSURE

• CLOSURE OPTIMIZATION

can capture constants and variables from the surrounding context
in which it’s defined.

• CAPTURING VALUES

• CLOSURE EXPRESSION