$ERR

References: - Error Handling - Object Methods

If an operation results in an error, the $ERR data type is returned. Check using the type function: if (result.type() == $ERR) something;

Under the hood, the $ERR type is a $LIST, and the same commands can be used to get more details on the error.

Creating $ERR Types

There are three ways to create $ERR types:

1. Direct Construction

x = $ERR();  /* Creates empty error object */
x.type();    /* $ERR */
x;           /* {} */

2. Runtime Errors

x = 9 / 0;   /* Division by zero creates error */
x.type();    /* $ERR */
x;           /* {"error":-1} */

3. Type Conversion with .err()

z = {"error": 43, "info": [3, 4]}.err();  /* Convert $LIST to $ERR */
z.type();    /* $ERR */
z;           /* {"error": 43, "info": [3, 4]} */

Error Object Manipulation

Error objects can be modified like any other object:

x = $ERR();
x ++= {error: 55, comment: 'test error'};
x;  /* {"error": 55, "comment": "test error"} */
x.type();  /* $ERR */

iferr(new)

If value is $ERR type, the new is used. Otherwise the value is used.

(10/2).iferr(55)  /* -> 5 */
(10/0).iferr(55)  /* -> 55 */

Error Handling Patterns

/* Check for errors */
result = some_operation();
if (result.type() == $ERR) {
    /* Handle error */
    result.error.echo();  /* Print error code */
} else {
    /* Use result */
}

/* Use iferr for simple fallback */
result = some_operation().iferr(default_value);