Bool

Built-in type · Written true or false

A Bool is one of two values, true or false. Comparisons give one, and if and while need one to decide what to do.

const age = 15
const raining = false
const teenager = 13 <= age <= 19      # → true

if teenager and not raining {
    print("Off to the park")
}

A condition must be a Bool. Emerald has no values that count as true or false on their own, so if count is an error; write what you mean, such as if count > 0.

At a glance

Showing as text
to_string()	"true" or "false"

Operators

Operator	Meaning	Example
and	Both are true	true and false → false
or	At least one is true	true or false → true
not	The opposite	not true → false
== !=	Compare	true != false → true

and and or stop as soon as the answer is known: in false and ready(), ready() is never called, and in true or ready(), it is not called either. Use this to check that something is safe before using it, as in index < items.count and items[index] > 0.

Emerald writes these operators as words. !, &&, and || are errors that point to not, and, and or.

Comparisons give a Bool, and they can be chained: 0 <= score <= 100 means 0 <= score and score <= 100. Two Bools cannot be ordered with < or >.

Showing as text

to_string(): String

"true" or "false", exactly as print shows it.

true.to_string()   # → "true"