Logical Types

Edit pageLast modified: 02 February 2025

The TypeLang, like PHP, supports two types of composite (logical) types: Union and Intersection. The ability to specify a nullable type using a separate expression is also supported.

Union Types

Each union type is separated by a pipe character (|) and may contain any other type definition.

tip

A | B | C

OR

OR

OR

A | B | C

A

B

C

Intersection Types

Each intersection type is separated by an ampersand character (&) and may contain any other type definition.

tip

A & B & C

AND

AND

AND

A & B & C

A

B

C

Nullable Types

Nullable type is a shortened alias for union type T | null and is written as ?T.

tip

Description of nullable type Example (equivalent to Example | null)

?Example

OR

OR

?Example

Example | null

Example

null

Parentheses

Parentheses can be used to disambiguate types.

tip

Disjunctive form (DNF).

(A & B) | C

OR

AND

AND

OR

( A & B ) | C

A & B

A

B

C

tip

Conjunctive form (CNF).

(A | B) & C

AND

OR

OR

AND

( A | B ) & C

A | B

A

B

C