Existence Operators perform operations to do with the existence of Variables.
| Symbol | Type | Name | Description | Example |
|---|---|---|---|---|
| ??? | Prefix | Existence | Returns true if the variable exists, or false otherwise | ??? a |
| destroy | Prefix | Destruction | Destroys the Variable (or Array key) named | destroy a |
Existence operators will only function on Variables. In particular, an error will be generated if destroy is applied to a Variable that does not exist.
The ERR Logical Operator - |?| - is essentially a convenient, in-line existence check, and is the logical comparison version of ???.