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Could you tell me when to use throw, exit and error?
1> catch throw ({aaa}).
{aaa}
2> catch exit ({aaa}).
{'EXIT',{aaa}}
3> catch gen_server:call(aaa,{aaa}).
{'EXIT',{noproc,{gen_server,call,[aaa,{aaa}]}}}
4> catch exit("jaj")
{'EXIT',"jaj"}
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catch statement with having throw Error(). This code will do that the 'msg' error is thrown in the try-block which will be get executed by catch statements. new Error object: It captures several properties of the place where the error happened. It exposes an error event with two parameters name & message.
It does, yes.
Exceptions should be used for exceptional situations outside of the normal logic of a program. In the example program an out of range value is likely to be fairly common and should be dealt with using normal if-else type logic. (See the programming exercises.)
Throwing an error lets you indicate that something unexpected happened and the normal flow of execution can't continue. You use a throw statement to throw an error.
There are 3 classes which can be caught with a try ... catch: throw, error and exit.
throw is generated using throw/1 and is intended to be used for non-local returns and does not generate an error unless it is not caught (when you get a nocatch error).
error is generated when the system detects an error. You can explicitly generate an error using error/1. The system also includes a stacktrace in the generated error value, for example {badarg,[...]}.
exit is generated using exit/1 and is intended to signal that this process is to die.
The difference between error/1 and exit/1 is not that great, it more about intention which the stacktrace generated by errors enhances.
The difference between them is actually more noticeable when doing catch ...: when throw/1 is used then the catch just returns the thrown value, as is expected from a non-local return; when an error/1 is used then the catch returns {'EXIT',Reason} where Reason contains the stacktrace; while from exit/1 catch also returns {'EXIT',Reason} but Reason only contains the actual exit reason. try ... catch looks like it equates them, but they are/were very different.
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