Null object

editable example

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ghul

use IO.Std.write_line

is_null(text: string?) -> bool => !text?

is_null(number: int?) -> bool => !number?

describe(text: string?) -> string =>

if let value = text then "\"{value}\"" else "null" fi

describe(number: int?) -> string =>

if let value = number then "{value}" else "null" fi

let ►text: string? = "hello"

let nothing: string? = null

let ►number: int? = 42

let no_number: int? = null

write_line("text is null: {is_null(text)}")

write_line("nothing is null: {is_null(nothing)}")

write_line("number is null: {is_null(number)}")

write_line("no_number is null: {is_null(no_number)}")

write_line("")

write_line("text: {describe(text)}")

write_line("nothing: {describe(nothing)}")

write_line("number: {describe(number)}")

write_line("no_number: {describe(no_number)}")

write_line("")

write_line("nothing, with a fallback: {nothing ?? "none"}")

text is null:      False
nothing is null:   True
number is null:    False
no_number is null: True

text:      "hello"
nothing:   null
number:    42
no_number: null

nothing, with a fallback: none