Panic in Pascal

program PanicExample;

uses
  SysUtils;

procedure CreateFile(filename: string);
var
  f: TextFile;
begin
  AssignFile(f, filename);
  try
    Rewrite(f);
  except
    on E: Exception do
    begin
      writeln('Error creating file: ', E.Message);
      Halt(1);
    end;
  end;
end;

begin
  // We'll use exceptions throughout this site to check for
  // unexpected errors. This is the only program on the
  // site designed to raise an exception.
  raise Exception.Create('a problem');

  // A common use of exceptions is to abort if a function
  // returns an error that we don't know how to
  // (or want to) handle. Here's an example of
  // raising an exception if we get an unexpected error when creating a new file.
  CreateFile('/tmp/file');
end.

In Pascal, we don’t have a direct equivalent to Go’s panic function. Instead, we use exceptions to handle unexpected errors or to fail fast. The raise statement is used to manually throw an exception, which is similar to calling panic in Go.

Running this program will cause it to raise an exception, print an error message, and exit with a non-zero status.

$ fpc panicexample.pas
$ ./panicexample
a problem

When the first exception in begin is raised, the program exits without reaching the rest of the code. If you’d like to see the program try to create a temp file, comment out the first raise statement.

Note that unlike some languages which use exceptions for handling of many errors, in Pascal it’s common to use function results or output parameters to indicate errors where possible, reserving exceptions for truly exceptional circumstances.

Pascal’s exception handling mechanism allows for more structured error handling compared to Go’s panic/recover model. You can use try-except blocks to catch and handle specific types of exceptions, providing more granular control over error handling.

Remember that while this example demonstrates how to simulate Go’s panic behavior in Pascal, it’s generally better to use Pascal’s built-in error handling mechanisms and coding practices for most situations.