These functions can be used in external code with OpenMaple or define_external.

These functions raise the Maple error described by msg, equivalent to the Maple command error(msg,arg1,arg2);.

If used as part of ExternalCalling, execution is returned back to Maple (or to the exception handler installed by a try command).  If used as part of OpenMaple, the errorCallBack is invoked, and execution continues at the next statement. The OpenMaple behavior can be changed to interrupt computation at an error invoked by MapleRaiseError when the external function is launched via MapleTrapError.

The character string msg can contain wildcards of the form %N, where N is a non-zero integer. These wildcards are replaced by the extra argument, arg1 or arg2, before displaying the message. If %-N is specified, then the optional argument is displayed with the appropriate suffix, st, nd, rd, or th, appended. For example, consider the following command.

This, if invoked, raises the error, "the 4th argument, 'foo', is not valid", assuming i=4, and args[i] is set to the Maple name, foo. For more information, see error. The only option not allowed is %0 since the function cannot determine the number of unparsed optional arguments.

$\mathrm{with}\left(\mathrm{ExternalCalling}\right)\:$

$\mathrm{dll}≔\mathrm{ExternalLibraryName}\left(''HelpExamples''\right)\:$

$\mathrm{err}≔\mathrm{DefineExternal}\left(''MyGuessInput''\,\mathrm{dll}\right)\:$

$\mathrm{err}\left(\right)$

Error, (in err) one argument expected

$\mathrm{err}\left(\left[0\,0\right]\right)$

Error, (in err) integer expected for M_INT parameter

$\mathrm{err}\left(-1\right)$

Error, (in err) -1 is too small

$\mathrm{err}\left(99\right)$

Error, (in err) 99 is too big

$\mathrm{err}\left(1\right)$

$\mathrm{true}$