$boolean
Signature: $boolean(arg)
Parameters:
- arg - An argument to be cast to a Boolean.
Casts the argument to a Boolean using the following rules:
| Argument type | Result |
|---|---|
| Boolean | unchanged |
| string: empty | false |
| string: non-empty | true |
| number: 0 | false |
| number: non-zero | true |
| null | false |
| array: empty | false |
| array: contains a member that casts to true | true |
| array: all members cast to false | false |
| object: empty | false |
| object: non-empty | true |
| function | false |
$not
Signature: $not(arg)
Parameters:
- arg - An argument to be cast to a Boolean and inverted.
Returns Boolean NOT on the argument. arg is first cast to a boolean.
$exists
Signature: $exists(arg)
Parameters:
- arg - An argument to chech the existence of.
Returns Boolean true if the arg expression evaluates to a value, or false if the expression does not match anything (e.g. a path to a non-existent field reference).
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