R – Who invented the throw/try/catch[/finally] kind of error handling

exceptionexception handlinglanguage-designlanguage-featurestheory

My questions are more of historical nature than practical:

Who invented it?
Which language used it first (and to what extent)?
What was the original idea, the underlying concept (which actual problems had to be solved these days, papers welcome) ?
Is LISPs condition system the ancestor of current exception handling?

Best Answer

Today's Common Lisp condition system is a relative newcomer. The design was based on previous systems, but wasn't included as part of the Common Lisp language until the late 80's around the time of CLTL2

I believe the conditions chapter in that book has a fair amount commentary on the history and background of the design, and references to related research and prior implementations of similar systems.

Related Solutions

Java – Why aren’t variables declared in “try” in scope in “catch” or “finally”

Two things:

Generally, Java has just 2 levels of scope: global and function. But, try/catch is an exception (no pun intended). When an exception is thrown and the exception object gets a variable assigned to it, that object variable is only available within the "catch" section and is destroyed as soon as the catch completes.
(and more importantly). You can't know where in the try block the exception was thrown. It may have been before your variable was declared. Therefore it is impossible to say what variables will be available for the catch/finally clause. Consider the following case, where scoping is as you suggested:
```
try
{
    throw new ArgumentException("some operation that throws an exception");
    string s = "blah";
}
catch (e as ArgumentException)
{  
    Console.Out.WriteLine(s);
}
```

This clearly is a problem - when you reach the exception handler, s will not have been declared. Given that catches are meant to handle exceptional circumstances and finallys must execute, being safe and declaring this a problem at compile time is far better than at runtime.

C# – Why is try {…} finally {…} good; try {…} catch{} bad

The big difference is that try...catch will swallow the exception, hiding the fact that an error occurred. try..finally will run your cleanup code and then the exception will keep going, to be handled by something that knows what to do with it.

Best Answer

Related Solutions

Java – Why aren’t variables declared in “try” in scope in “catch” or “finally”

C# – Why is try {…} finally {…} good; try {…} catch{} bad

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