Custom Errors in Wolfram Language

Our custom error example demonstrates how to create and use custom error types. Here’s the full implementation:

(* Define a custom error type *)
argError[arg_, message_] := <|"arg" -> arg, "message" -> message|>

(* Define an error message function *)
errorMessage[error_] := ToString[error["arg"]] <> " - " <> error["message"]

(* Define the main function *)
f[arg_] := Module[{},
  If[arg == 42,
    (* Return our custom error *)
    Throw[argError[arg, "can't work with it"]],
    (* Return the result *)
    arg + 3
  ]
]

(* Main execution *)
result = Catch[
  f[42],
  _,
  (* Error handling *)
  Module[{err = #1},
    If[MatchQ[err, _argError],
      Print[err["arg"]];
      Print[err["message"]],
      Print["err doesn't match argError"]
    ]
  ] &
]

In Wolfram Language, we don’t have a built-in error system like in some other languages. Instead, we use the Throw and Catch mechanism for exception handling. Here’s how our implementation works:

1. We define a custom error type argError as an association with arg and message fields.

2. The errorMessage function is defined to format our custom error message.

3. The f function demonstrates how to use our custom error. If the input is 42, it throws our custom error.

4. In the main execution, we use Catch to handle any thrown errors.

5. If an error is caught, we check if it matches our argError pattern. If it does, we print the arg and message fields. Otherwise, we print a generic error message.

To run this program, you can copy it into a Wolfram Language notebook or file and evaluate it. The output should be:

42
can't work with it

This example demonstrates how to implement and use custom error types in Wolfram Language, providing a way to handle specific error conditions in your code.