mixed catch(expr, expr, ...)
mixed catch(expr, expr, ... ; modifiers)
Evaluate the expressions. If there is no error, 0 is returned.
If there is an error, the evaluation of the expressions stops at
that point, and a string with the error message is returned.
System error messages start with a leading '*', user-defined
error values (other than 0) as given to throw() and raise_error() are
returned as they are.
If at the time the catch() is encountered less than
__CATCH_EVAL_COST__ eval ticks are left, a runtime error will be
thrown from inside the catch() (and thus caught like every other
error) and the expressions will not be executed. The 'reserve'
modifier can be used to reserve a different amount of eval ticks.
The default behaviour of catch() can be changed using modifiers:
'nolog': Normally, the caught error will be logged in the
error logs for easier debugging. With this
modifier, the log is suppressed.
'publish': Normally, master::runtime_error() is not called
for a caught error. This modifier instructs
catch() to call it nevertheless.
'reserve <expr>': The expression has to evaluate to a number
greater than 0 and is used to determine the amount
of eval ticks to reserve, instead of the default
of __CATCH_EVAL_COST__. The minimum required
are 2 * __MASTER_EVAL_COST__.
catch() itself is not expensive as far as execution time is
concerned: it is about the same as a intra-object function call.
throw() is not very expensive either, but does include the
internal cleanup of several structures.
Real runtime errors on the other hand are expensive regardless
of whether they are caught or not, as they include the generation
of the stack backtrace.
catch() is not really an efun but a compiler directive.
if (err = catch(obj = clone_object("/foo/bar/baz")))
write("Cannot clone object, reason:"+err"+\n");
LDMud 3.2.9 introduced the 'nolog' catch() as experimental feature.
LDMud 3.2.10 implemented 'nolog' as official form and added
LDMud 3.3.559 moved the check regarding __CATCH_EVAL_COST__ inside
LDMud 3.3.560 added the 'reserve' modifier.
throw(E), raise_error(E), predefined(D), runtime_error(M)