Bool

bool confirms that a value is a boolean and returns it unchanged.

Overview

Use bool when a value must already be either true or false:

is_ready | true.bool

:say(is_ready)  /// true

is_ready | true.bool

:say(is_ready)  /// true

bool is a strict cast. It does not guess whether another kind of value should mean true or false.

Method Style

The usual casting style places .bool after the value:

enabled | true.bool
disabled | false.bool

enabled | true.bool
disabled | false.bool

The method form does not need parentheses.

The equivalent free-call form is:

enabled | bool(true)

enabled | bool(true)

Both forms behave the same way.

Strict Boolean Values

Only actual boolean values are accepted:

true.bool   /// true
false.bool  /// false

true.bool   /// true
false.bool  /// false

Numbers are not converted to booleans:

1.bool
/// error: R0215 type-lock-cast

1.bool
/// error: R0215 type-lock-cast

Strings are not converted either:

"true".bool
/// error: R0215 type-lock-cast

"true".bool
/// error: R0215 type-lock-cast

This prevents values such as 1, 0, "yes", and empty strings from silently receiving a meaning the program did not state.

Parsing Boolean Text

Use Parse Bool when a string should be interpreted as a boolean:

answer | "true".parse_bool

:say(answer)  /// true

answer | "true".parse_bool

:say(answer)  /// true

bool checks or casts a boolean value. parse_bool reads a boolean from text.

Arrays and Maps

When given an array, bool checks every value and returns a new array:

flags | [true, false, true].bool

flags | [true, false, true].bool

When given a map, bool checks every value and keeps the keys unchanged:

settings | {
    music: true,
    subtitles: false
}.bool

settings | {
    music: true,
    subtitles: false
}.bool

Every value in the collection must already be a boolean:

[true, 1, false].bool
/// error: R0215 type-lock-cast

[true, 1, false].bool
/// error: R0215 type-lock-cast

The original collection is not changed.

Signature

value.bool
bool(value)

value.bool
bool(value)

bool returns the boolean unchanged, or returns a collection containing the checked boolean values.

Errors

bool requires exactly one value:

bool()
/// error: R0301 wrong-arity

bool()
/// error: R0301 wrong-arity

The value must already be a boolean:

bool("false")
/// error: R0215 type-lock-cast

bool("false")
/// error: R0215 type-lock-cast

Every value inside an array or map must also be a boolean.