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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: time |
| Date | 2012-11-19 23:54 -0800 |
| Organization | None to speak of |
| Message-ID | <lnd2z8r9oe.fsf@nuthaus.mib.org> (permalink) |
| References | <k8ehrs$ddf$1@dont-email.me> <4hjla8hdbe4ft1vjnnv6ppdqd08odelkbg@4ax.com> <lnd2z9f65y.fsf@nuthaus.mib.org> <k8el52$u6c$1@dont-email.me> |
"Bill Cunningham" <nospam@nspam.invalid> writes:
> Keith Thompson wrote:
>> Geoff <geoff@invalid.invalid> writes:
>>> On Mon, 19 Nov 2012 19:11:41 -0500, "Bill Cunningham"
>>> <nospam@nspam.invalid> wrote:
>>>> I am using the time and date in my code using asctime () time(),
>>>> and localtime(). I know in POSIX they are obsolete but I am
>>>> concerned with c89-99. strftime() is suppoed to be the function
>>>> used now. I get the time and date just fine with the code I've
>>>> written but I want to use the time to seed a random number
>>>> generator. I don't know if I want seconds from epoch or what. Any
>>>> input?
>>>
>>> srand((unsigned)time(NULL));
>>
>> The cast is unnecessary. time() returns a value of type time_t,
>> which is an arithmetic type; it will be implicitly converted to
>> the appropriate type for the argument to srand() (which, yes,
>> happens to be unsigned int).
> [snip]
>
> An arithmetic type? So what are you trying to say exactly in simple terms?
> This is an example of where I can pick up knowledge. Are you saying with
> "arithmetic types" casts aren't necessaary?
An arithmetic type is either an integer type or a floating-point
type (or a complex or imaginary type, but don't worry about those).
N1570 6.2.5p18.
If you assign a value of any arithmetic type to an object of
any arithmetic type (or initialize it, or pass it as a function
argument), the value will be implicitly converted to the target type.
N1570 6.5.16.1p1, first bullet. There are also implicit conversions
for other kinds of expressions, with more complicated rules; such
conversions *usually* do the right thing, but sometimes you might
need a cast to enforce a particular conversion.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Will write code for food.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-19 19:11 -0500
Re: time Geoff <geoff@invalid.invalid> - 2012-11-19 16:26 -0800
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-19 16:51 -0800
Re: time Geoff <geoff@invalid.invalid> - 2012-11-19 17:01 -0800
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-19 20:07 -0500
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-19 23:54 -0800
Re: time pete <pfiland@mindspring.com> - 2012-11-20 07:31 -0500
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-20 17:09 -0500
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-19 16:30 -0800
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-19 20:04 -0500
Re: time Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-11-25 05:52 -0800
Re: time Nobody <nobody@nowhere.com> - 2012-11-20 03:07 +0000
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-19 23:58 -0800
Re: time Anand Hariharan <mailto.anand.hariharan@gmail.com> - 2012-11-21 08:30 -0800
Re: time "osmium" <r124c4u102@comcast.net> - 2012-11-21 11:11 -0600
Re: time James Kuyper <jameskuyper@verizon.net> - 2012-11-21 12:22 -0500
Re: time gof@somewhere.invalid (Adam Wysocki) - 2012-11-21 19:09 +0000
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-21 12:01 -0800
Re: time gof@somewhere.invalid (Adam Wysocki) - 2012-11-23 08:15 +0000
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-21 15:16 -0500
Re: time "osmium" <r124c4u102@comcast.net> - 2012-11-21 14:23 -0600
Re: time Rosario1903 <Rosario@invalid.invalid> - 2012-11-22 10:25 +0100
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-21 12:30 -0800
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-21 18:24 -0500
Re: time Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-11-25 05:56 -0800
Re: time Nobody <nobody@nowhere.com> - 2012-11-22 02:00 +0000
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-21 19:57 -0800
Re: time gof@somewhere.invalid (Adam Wysocki) - 2012-11-23 08:31 +0000
Re: time army1987 <army1987@ask-for-it.invalid> - 2012-11-24 13:58 +0000
Re: time Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-11-22 11:36 +0000
Re: time gof@somewhere.invalid (Adam Wysocki) - 2012-11-23 08:20 +0000
Re: time Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-11-23 14:31 +0000
Re: time Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-11-25 05:54 -0800
Re: time Mark Storkamp <mstorkamp@yahoo.com> - 2012-11-20 08:34 -0600
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-20 20:37 -0500
Re: time Keith Thompson <kst-u@mib.org> - 2012-11-20 20:25 -0800
Re: time "Bill Cunningham" <nospam@nspam.invalid> - 2012-11-21 15:11 -0500
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