Advanced Programming Guide

7.2 Using Compiled Code in Maple • 331example, if you create the number num = one-billion, then you computethe number val = 2*500-million. An address comparison of numand val does not indicate equality. After calling simplify as in num =MapleUnique(kv,num), both num and val point to the same memory.The following functions raise a Maple software-style er-Error Handlingror message.void MapleRaiseError( MKernelVector kv, char *msg );void MapleRaiseError1( MKernelVector kv, char *msg,ALGEB arg1 );void MapleRaiseError2( MKernelVector kv, char *msg,ALGEB arg1, ALGEB arg2 );The Fortran equivalent is:SUBROUTINE maple_raise_error( kv, msg, len )These functions display the message msg, stop execution, and returnto the Maple input loop. A call to MapleRaiseError does not return.The character string msg can contain wildcards of the form %N, where Nis a non-zero integer. These wildcards are replaced by the extra argument,arg1 or arg2, before displaying the message. If %-N is specified, then theoptional argument is displayed with st, nd, rd, or th appended to it. Forexample:MapleRaiseError2(kv, "the %-1 argument, ’%2’, is not valid",ToMapleInteger(i), args[i]);This, if invoked, raises the error, "the 4th argument, ’foo’, is notvalid", assuming i=4, and args[i] is set to the Maple name foo. 4The only option not allowed is %0 since the function cannot determinethe number of unparsed optional arguments.The C API also provides a mechanism for trapping errors raised byMaple.void* MapleTrapError( MKernelVector kv, void *(*proc)P(( void *data )), void *data, M_BOOL *errorflag );MapleTrapError executes the C function proc, passing it the data,data. If an error occurs, errorflag is set to TRUE and traperror returns4 For more information, see ?error.