Skip to content

Error library#

Importing#

|#| 'stderr.nest' = err

Functions#

@try#

Synopsis:

[func: Func, args: Array|Vector, catch_exit: Bool?] @try -> Map

Description:

Calls func passing args as the arguments and catching any errors that might occur. If catch_exit is null it defaults to false.

Arguments:

  • func: the function to be called
  • args: the arguments to be passed to the function
  • catch_exit: whether the function should catch the error raised by exit

Returns:

A map containing value, error and traceback:

  • value is the value returned by the function or null if an error occurred.
  • error is null if everything was successful otherwise it is a map containing name, message and pos.
  • traceback is an array of positions that trace back the cause of the error.

A position is a map that contains 3 keys:

  • file is the path of the file that the position refers to
  • start is an array of length 2 with the first number being the line and the second being the column of the start of the interested expression
  • end is also an array with the line and column of the end of the expression

Note

The lines start from 0 and the columns from 1 and the end position is inclusive.

Example:

The file example.nest contains this code: 

|#| 'stderr.nest' = err

#f ["Random Error" !! "hello this is a message"]
#g [@f]
>>> (g {,} @err.try)

The formatted output looks like this:

{
    'value': null,
    'error': {
        'name': 'Random Error',
        'message': 'hello this is a message',
        'pos': {
            'file': 'example.nest',
            'start': {2, 4},
            'end': {2, 46}
        }
    },
    'traceback': {
        {
            'file': 'example.nest',
            'start': {3, 4},
            'end': {3, 5}
        }
    }
}

Constants#

Note

The messages used inside the interpreter are not available as they are not created in advance.

CALL_ERROR#

This is the string used by Nest when throwing call errors.

IMPORT_ERROR#

This is the string used by Nest when throwing import errors.

MATH_ERROR#

This is the string used by Nest when throwing math errors.

MEMORY_ERROR#

This is the string used by Nest when throwing memory errors.

SYNTAX_ERROR#

This is the string used by Nest when throwing syntax errors.

TYPE_ERROR#

This is the string used by Nest when throwing type errors.

VALUE_ERROR#

This is the string used by Nest when throwing value errors.