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Date: Fri, 28 Feb 2014 22:08:03 +1100
Subject: Re: Can global variable be passed into Python function?
From: Chris Angelico <rosuav@gmail.com>
Cc: "python-list@python.org" <python-list@python.org>
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On Fri, Feb 28, 2014 at 9:02 PM, Marko Rauhamaa <marko@pacujo.net> wrote:
> PS On the topic of enums, when are we getting support for a switch
> statement?

I don't see that they're particularly connected. In my C code, I've
used enums frequently as quick constants, often never switching on
them. Conversely, I often use switch in C code with either integer or
character constants. (ASCII character, of course, as that's all you
get.) Take this, for example, from my C++ MUD client:

enum {IS=0x00,ECHO=0x01,SEND=0x01,SUPPRESSGA=0x03,TERMTYPE=0x18,NAWS=0x1F,SE=0xF0,GA=0xF9,SB,WILL,WONT,DO=0xFD,DONT,IAC=0xFF};

That one happens to be used in a switch at one point, but it's also
used in other ways, like this:

static char naws[]={IAC,SB,NAWS,0,0,0,0,IAC,SE};

(The actual window size gets patched in separately, in case you're
curious... but I suspect most people here won't be aware that IAC SB
NAWS means Interpret-As-Command, Subnegotiation Begin, Negotiate About
Window Size, and that this is a TELNET command sequence.)

With bit flags, they'll never be used in switch:

enum //Bitflags in hackity
{
    HACK_ATAT=1, //Perform @@ -> fill-in translation
    HACK_AUTOEDIT=2, //Respond to the autoedit markers [now active by default]
};

...

if (hackity&HACK_ATAT) ...

Sometimes, they're just states, and they're assigned and/or compared
for equality:

enum {ic, court, citizen, trivia, sports, chancount} lastlinetype;

Some things check if (lastlinetype == ic), but nothing ever switches on it.

Meanwhile, here's a switch block from Gypsum that will never use enumerations:

switch (max(delay,base))
{
    case 0..59: ... handling for <1 minute ...
    case 60..3599: ... handling for <1 hour ...
    default: ... handling for >= 1 hour ...
}

No, the features are quite independent. Python currently has dispatch
tables and if/elif chains, and a strong cultural aversion to switch.
You could change that by coming up with some *really* awesome
proposal, but you'll be fighting against the tide a bit.

ChrisA