[Numpy-discussion] Python needs goto

[Charles R Harris]

On Fri, Sep 25, 2015 at 10:27 AM, Anne Archibald <archibald at astron.nl>
wrote:

> goto! and comefrom! Together with exceptions, threads, lambda, super,
> generators, and coroutines, all we're lacking is
> call-with-current-continuation for the full list of impenetrable
> control-flow constructs. Oh, and lisp-style resumable exception handling.
> (Suggested syntax: drop(exception, value) to return control to where the
> exception was raised and make the raise statement return value.)
>
> On Thu, Sep 24, 2015 at 8:42 PM Charles R Harris <
> charlesr.harris at gmail.com> wrote:
>
>> On Thu, Sep 24, 2015 at 12:13 PM, Yarko Tymciurak <yarkot1 at gmail.com>
>> wrote:
>>
>>>
>>>
>>> I think there are more valid uses - I've read that "goto" basically is
>>> what a state machine does.
>>> Have a read of the brief implementation notes for "goto" in golang, for
>>> example.  Goto may not be unreasonable to use, just most people would
>>> abuse.  Sort of like "everyone shouldn't write assembly, but if you
>>> understand the machine, you can make good things happen".  Without
>>> compiler/interpreter checks, more responsibility rests on the coder to keep
>>> out of trouble.
>>>
>>
>> I would agree about state machines. When implemented using the standard
>> control flow constructs they always look a bit artificial.
>>
>>
> That depends what your "standard" control flow constructs are. Has anyone
> tried implementing a state machine using coroutines? They seem like a
> rather natural setup: each state is a coroutine that loops, doing the
> appropriate actions for the state and then handing control over to the
> coroutine for the next state.
>
>
Might well do. TAOCP has an example elevator, passenger simulation that,
IIRC, used coroutines. I think I may have even once used a language that
had them (Algol 68?). It will be interesting to see what their inclusion in
Python 3.5 leads to.

Chuck
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