Make a type optional

Shorthand for T | NULL, and the readable way to write a self-reference or a forward reference by name.

Usage

opt(t)

Arguments

t

A type, or a struct name.

Value

A type.

Examples

opt(int[1])(NULL)
#> NULL
opt(int[1])(3)
#> [1] 3
opt("User")
#> <type> User | NULL