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Re: Comparison Style

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On Fri, Apr 26, 2013 at 12:37 PM, Dennis Lee Bieber
<wlfraed@ix.netcom.com> wrote:
> On Thu, 25 Apr 2013 15:57:49 +1000, Chris Angelico <rosuav@gmail.com>
> declaimed the following in gmane.comp.python.general:
>> It's conventional to compare variables to constants, not constants to
>> variables (even in C where there's the possibility of mucking up the
>> operator, most people still compare variables to constants).
>
>         The main reason for /literal/ first is to trap C/C++ assignment as
> expression.
>
>         if (x = 5)
>
> ends up assigning x the value 5 and THEN, since 5 is "true" executing
> the "then" part.
>
>         if (5 = x)
>
> OTOH is a compiler error.
>

Aware of this. My point is that, even though there's a good reason for
putting the constant first, it's still FAR more common to put the
variable first. Also, this protection helps only when the "constant"
is actually something the compiler knows is a constant - it doesn't
work in a search function, for instance:

char *strchr(char *string, char findme) {
    while (*string) {
        if (*string==findme) return string;
        ++string;
    }
    return 0;
}

If you switch the order of operands in that, the compiler won't help
you. Plus it "reads" wrong. So the convention is still
variable==constant.

ChrisA

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Comparison Style llanitedave <llanitedave@veawb.coop> - 2013-04-24 22:49 -0700
  Re: Comparison Style Chris Angelico <rosuav@gmail.com> - 2013-04-25 15:57 +1000
    Re: Comparison Style llanitedave <llanitedave@veawb.coop> - 2013-04-25 07:19 -0700
      Re: Comparison Style Chris Angelico <rosuav@gmail.com> - 2013-04-26 02:25 +1000
      Re: Comparison Style Steve Simmons <square.steve@gmail.com> - 2013-04-25 19:31 +0100
        Re: Comparison Style llanitedave <llanitedave@veawb.coop> - 2013-04-25 13:13 -0700
          Re: Comparison Style Neil Cerutti <neilc@norwich.edu> - 2013-04-25 20:15 +0000
          Re: Comparison Style Steve Simmons <square.steve@gmail.com> - 2013-04-25 21:35 +0100
          Re: Comparison Style Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-04-26 10:02 +0100
  Re: Comparison Style Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-04-25 22:37 -0400
  Re: Comparison Style Chris Angelico <rosuav@gmail.com> - 2013-04-26 12:48 +1000
    Re: Comparison Style Roy Smith <roy@panix.com> - 2013-04-27 17:03 -0400
      Re: Comparison Style Terry Jan Reedy <tjreedy@udel.edu> - 2013-04-27 17:40 -0400
  Re: Comparison Style Dave Angel <davea@davea.name> - 2013-04-25 23:43 -0400

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