Goto (Posting On Python-List Prohibited)
bartc
bc at freeuk.com
Sun Dec 31 18:21:05 EST 2017
On 31/12/2017 22:09, Ben Bacarisse wrote:
> No, you missed the point and did not address the question. You said (now
> cut)
>
> | If I thought introducing functions, whether local or not, as a way of
> | avoiding goto was worth doing, I would do so.
>
> but I'm not sure you know if it's worth it or not. So here's my
> question again: what language (or languages) were you using when you
> concluded that it was not worth using local functions to avoid gotos?
> Maybe you had a bad experience from some language that did it badly.
What makes you think I had a bad experience? I posted a version using
Python a few hours ago (which needs the local function to be moved to
work properly).
The same example works in my language (one of them anyway), but I still
find a quick goto the simplest thing to do especially when the code is
not complete so I don't know what will be added or changed or moved,
which will be harder as soon a specific sequence is extracted into a
function.
Also, what would be the duplicated code is seen to 'belong' to one of
the options, rather than be anonymous.
(Here is the same example in my static language:
https://pastebin.com/raw/dX2FNK7a
fn1 uses goto. fn2 uses a local function (not very demanding here so it
works). fn3 uses the special 'block-call' feature which I no longer use
(but I haven't yet got rid of it).
I prefer fn1 and fn3 because the code stays inline. If I had some
inspiration for a better feature then I'd have fn4 and maybe fn5 too.)
Within Python, I touched on performance issues in my earlier post. (A
local function apparently involves an extra assignment - per function -
each time the containing function is called.)
>> (Which is likely to cause problems if the code includes breaks, or
>> gotos if the language has them.)
>
> Good grief! That is exactly the sort of code you should not re-use by
> jumping to it. There are myriad potential problems and putting the code
> into a function will allow the compiler to diagnose lots of them.
OK, forget the gotos then. But a block can still contain break or return
(and in my syntax, several other loop controls). It loses context as
soon as it's hoisted into a function.
--
bartc
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