2.7.1 C Reference

Macro: ECL_HANDLER_CASE ¶

C macro for handler-case

Synopsis

ECL_HANDLER_CASE_BEGIN(env,names) {

} ECL_HANDLER_CASE(n,condition) { {

} ECL_HANDLER_CASE_END;

Description

ECL_HANDLER_CASE_BEGIN runs a block of C code with a set of error handlers bound to the names given by the list names. The subsequent ECL_HANDLER_CASE statements specify what to do when the n-th type of conditions is found, where n is an integer denoting the position of the name in the list names.

When a condition is signaled, ECL scans the list of signal handlers, looking for matches based on typep. If the match with the highest precedence belongs to the list names, ECL will perform a non-local transfer of control to the appropriate ECL_HANDLER_CASE, passing it a condition object as unique argument.

The following example shows how to establish a handler for error conditions. Note how the first value to ECL_HANDLER_CASE matches the position of the condition name in the list:

cl_object error = ecl_make_symbol("ERROR","CL");
ECL_HANDLER_CASE_BEGIN(the_env, ecl_list1(error)) {
   /* This form is evaluated with bound handlers */
   output = cl_eval(1, form);
} ECL_HANDLER_CASE(1, condition) {
   /* This code is executed when an error happens */
   /* We just return the error that took place */
   output = condition;
} ECL_HANDLER_CASE_END;

Macro: ECL_RESTART_CASE ¶

C macro for restart-case

Synopsis

ECL_RESTART_CASE_BEGIN(env,names) {

} ECL_RESTART_CASE(n,args) { {

} ECL_RESTART_CASE_END;

Description

ECL_RESTART_CASE_BEGIN runs a block of C code with a set of restarts bound to the names given by the list names. The subsequent ECL_RESTART_CASE statements specify what to do when the n-th restart is invoked, where n is an integer denoting the position of the name in the list names.

When the restart is invoked, it can receive any number of arguments, which are grouped in a list and stored in a new variable created with the name args.

The following example shows how to establish an abort and a use-value restart. Note how the first value to ECL_RESTART_CASE matches the position of the restart name in the list:

cl_object abort = ecl_make_symbol("ABORT","CL");
cl_object use_value = ecl_make_symbol("USE-VALUE","CL");
ECL_RESTART_CASE_BEGIN(the_env, cl_list(2, abort, use_value)) {
   /* This form is evaluated with bound restarts */
   output = cl_eval(1, form);
} ECL_RESTART_CASE(1, args) {
   /* This code is executed when the 1st restart (ABORT) is invoked */
   output = ECL_NIL;
} ECL_RESTART_CASE(2, args) {
   /* This code is executed when the 2nd restart (USE-VALUE) is invoked */
   output = ECL_CAR(args);
} ECL_RESTART_CASE_END;

• ANSI dictionary