Re: Continuations (was google summer of code)

[HyperHacker <hyperhacker@...>]

On Tue, Feb 22, 2011 at 12:23, HyperHacker <hyperhacker@gmail.com> wrote:
> On Tue, Feb 22, 2011 at 11:52, Steve Litt <slitt@troubleshooters.com> wrote:
>> On Tuesday 22 February 2011 13:17:00 Pierre-Yves Gérardy wrote:
>>> > roberto> It always strike me why gotos are considered evil and ugly,
>>> > roberto> but continuations, which are a completely unrestricted form
>>> > roberto> of computed/assigned gotos, are considered beautiful. Maybe
>>> > roberto> the problem with gotos is that they are too restrictive?
>>>
>>> I think that the problem is social, not technical.
>>>
>>> Continuations are conceptually more complex, and as such are less
>>> likely to be abused by clueless people.
>>
>> This would be my guess also.
>>>
>>> The "considered evil" essay was necessary in its time because, outside
>>> accademia, goto was the dominant branching construct, ingrained in
>>> programming habits, and this was causing damage. Continuations never
>>> were popular enough to warrant such a rant.
>>
>> Yes. Any fool can use goto. Anyone in the business before 1985 has been forced
>> to deal with goto and understands on a gut level its horrors. As for myself, I
>> was TAUGHT to use gotos in college, along with that perverse matching design
>> tool, the flowchart. I was a terrible programmer. I wasn't able to become a
>> professional programmer until discovering return from subroutine and
>> functional decomposition in 1982.
>>
>>>
>>> By now, good practice are taught from day one, so I think that the
>>> Dijstra ban of the goto statement from structured languages and their
>>> descendants could be lifted without harm.
>>
>> I disagree. To paraphrase PT Barnum, there's an idiot born every minute.
>>
>> :-)
>>
>> SteveT
>>
>> Steve Litt
>> Recession Relief Package
>> http://www.recession-relief.US
>> Twitter: http://www.twitter.com/stevelitt
>>
>>
>>
>
> I think the biggest issue people have is that goto can easily be
> abused to create unreadable spaghetti code, whereas continue is a bit
> harder to misuse. Of course both can be used well and both can be used
> poorly, but goto makes it much easier to construct big tangled messes
> that become difficult to follow or debug.
> Goto also has some negative stigma attached to it, and so I fear
> people would look down on any language that encourages its use, even
> if it's used well.
>
> I also wonder, if Lua had goto, what syntax would define a label?
> "foo:" and ":foo" would both be ambiguous, and I'm having trouble
> thinking of anything else that wouldn't be ugly. Then as well there
> needs to be a mechanism for keeping track of those labels.
>
> In all my years of coding I've never found a need or desire to use
> goto, whereas continue is something I often find myself wishing when I
> have to write a loop like:
>
> while something() do
>        local x = foo()
>        if x then
>                --...many lines here...
>        end
> end
>
> as opposed to:
>
> while something() do
>        local x = foo()
>        if not x then continue end
>        --...many lines here...
> end
>
> The latter saves a level of indentation and avoids wrapping a large
> block in an if/end (which is especially troublesome in Lua since there
> are no braces for IDEs to match). While large blocks can usually be
> moved into functions (where you can then use return for a
> continue-like effect), this isn't always feasible especially if the
> large block is in fact several small blocks ending in conditional
> continues or nested blocks. Anyway, moving the loop body into a
> function means moving it outside the loop, which isn't terribly
> helpful for readability either.
>
> Though, I think the biggest reason people have for wanting continue is
> that we already have break, and the two go hand in hand. While named
> break and computed goto and other such nice features may be more
> useful, they'd also require bigger changes to the language; continue
> should only require a few added lines. (There's a patch on the wiki
> that adds it if someone wants to check that out.)
>
> --
> Sent from my toaster.
>

Hmm, I should learn to proofread. That first line should say "one of
the biggest issues".

-- 
Sent from my toaster.