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Christmas Quiz 2022

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  Christmas Quiz 2022 Roman P <invalid@example.com> - 2022-12-18 20:00 +0000
    Re: Christmas Quiz 2022 Tony Oliver <guinness.tony@gmail.com> - 2022-12-18 13:18 -0800
      Re: Christmas Quiz 2022 Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-18 16:48 -0800
      Re: Christmas Quiz 2022 Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-18 17:18 -0800
        Re: Christmas Quiz 2022 "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-19 19:39 -0800
      Re: Christmas Quiz 2022 Niles Rogoff <eternal-september@niles.xyz> - 2022-12-27 01:22 -0800
        Re: Christmas Quiz 2022 Öö Tiib <ootiib@hot.ee> - 2022-12-27 01:58 -0800
          Re: Christmas Quiz 2022 Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-27 10:25 -0800
        Re: Christmas Quiz 2022 James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-12-27 05:07 -0500
          Re: Christmas Quiz 2022 scott@slp53.sl.home (Scott Lurndal) - 2022-12-27 16:06 +0000
            Re: Christmas Quiz 2022 scott@slp53.sl.home (Scott Lurndal) - 2022-12-27 17:42 +0000
            Re: Christmas Quiz 2022 Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-27 13:53 -0800
      Re: Christmas Quiz 2022 Niles Rogoff <eternal-september@niles.xyz> - 2022-12-27 01:24 -0800
        Re: Christmas Quiz 2022 scott@slp53.sl.home (Scott Lurndal) - 2022-12-27 16:07 +0000
    Re: Christmas Quiz 2022 Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-18 21:22 +0000
      Re: Christmas Quiz 2022 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-12-18 21:40 +0000
      Re: Christmas Quiz 2022 Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-18 17:02 -0800
      Re: Christmas Quiz 2022 Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-18 17:20 -0800
    Re: Christmas Quiz 2022 red floyd <no.spam.here@its.invalid> - 2022-12-18 13:36 -0800
    Re: Christmas Quiz 2022 "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-18 13:48 -0800
      Re: Christmas Quiz 2022 Siri Cruise <chine.bleu@yahoo.com> - 2022-12-18 14:57 -0800
        Re: Christmas Quiz 2022 "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-18 15:43 -0800
          Re: Christmas Quiz 2022 Lynn McGuire <lynnmcguire5@gmail.com> - 2022-12-19 23:40 -0600
        Re: Christmas Quiz 2022 "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-12-20 14:01 -0800
    Re: Christmas Quiz 2022 Kaz Kylheku <864-117-4973@kylheku.com> - 2022-12-20 13:49 +0000
      Re: Christmas Quiz 2022 Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-20 14:33 +0000
        Re: Christmas Quiz 2022 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-12-20 14:44 +0000
          Re: Christmas Quiz 2022 Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-12-20 14:57 +0000
            Re: Christmas Quiz 2022 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-12-20 15:03 +0000
              Re: Christmas Quiz 2022 David Brown <david.brown@hesbynett.no> - 2022-12-20 16:32 +0100
              Re: Christmas Quiz 2022 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-12-20 15:41 +0000
                Re: Christmas Quiz 2022 Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-20 10:22 -0800
                  Re: for() syntax (Was: Christmas Quiz 2022) Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-12-20 18:54 +0000
                    Re: for() syntax Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-20 12:08 -0800
                    Re: for() syntax (Was: Christmas Quiz 2022) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-26 06:48 -0800
                  Re: Christmas Quiz 2022 Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-26 06:25 -0800
                Re: Christmas Quiz 2022 Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-26 06:24 -0800
                  Re: Christmas Quiz 2022 Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-12-26 13:05 -0800
    Re: Christmas Quiz 2022 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-12-20 12:46 -0800
      Re: Christmas Quiz 2022 Paavo Helde <eesnimi@osa.pri.ee> - 2022-12-20 23:49 +0200
        Re: Christmas Quiz 2022 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-12-20 14:00 -0800
          Re: Christmas Quiz 2022 Paavo Helde <eesnimi@osa.pri.ee> - 2022-12-21 00:13 +0200
            Re: Christmas Quiz 2022 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-12-20 14:38 -0800
      Re: Christmas Quiz 2022 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-12-20 21:31 -0800
        Re: Christmas Quiz 2022 David Brown <david.brown@hesbynett.no> - 2022-12-21 12:02 +0100

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#168574 — Christmas Quiz 2022

1) What happens when you divide an int variable by 0?
2) What happens when you divide a double variable by 0?
3) What happens when you overflow an int variable, that is, set it to a 
value beyond its range?
4) What is the difference between x = y++; and x = ++y;?
5) What is the difference between break, continue, and return when used 
inside a loop statement?
6) What are the three parts of a for statement and which of them are 
required?
7) What is the difference between the = and == operators?
8) Does the following statement compile?

for ( ; ; ) ;

9) What does the underscore _ represent in a switch expression?

Merry Christmas to you all.

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#168575

On Sunday, 18 December 2022 at 20:22:16 UTC, Roman P wrote:
> 1) What happens when you divide an int variable by 0? 
Signal SIGFPE is raised.

> 2) What happens when you divide a double variable by 0? 
Either +Inf, -Inf or a Nan is yielded.

> 3) What happens when you overflow an int variable, that is, set it to a 
> value beyond its range? 
Undefined Behaviour.

> 4) What is the difference between x = y++; and x = ++y;? 
a) x receives the value of y *before* y is incremented.
b) x receives the value of y *after* it has been incremented.

> 5) What is the difference between break, continue, and return when used 
> inside a loop statement? 
a) break causes the loop to exit immediately.
b) continue causes the loop body to stop and returns to the loop test expression.
c) return exits the enclosing function immediately.

> 6) What are the three parts of a for statement and which of them are 
> required? 
a) initialisation.
b) continuation test expression.
c) state update, usually updating that which is tested in (b).

> 7) What is the difference between the = and == operators? 
If you don't know this by now, give up programming.
(Hints: assignment, equality)

> 8) Does the following statement compile? 
> for ( ; ; ) ; 
Yep. But your program will not get any further than this statement.

> 9) What does the underscore _ represent in a switch expression? 
Nothing.  It's a valid character in any identifier.

> Merry Christmas to you all.
And good luck to you trying to con somebody into giving you a job as a C programmer.

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#168586

Tony Oliver <guinness.tony@gmail.com> writes:
> On Sunday, 18 December 2022 at 20:22:16 UTC, Roman P wrote:
>> 1) What happens when you divide an int variable by 0? 
> Signal SIGFPE is raised.

Perhaps that what happened when you tried it, but that's a poor way to
determine what the standard requires.  The behavior is undefined.

>> 2) What happens when you divide a double variable by 0? 
> Either +Inf, -Inf or a Nan is yielded.

For an implementation that doesn't define __STDC_IEC_559__, the behavior
is undefined.  For one that does, it's more complicated.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */

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#168588

Tony Oliver <guinness.tony@gmail.com> writes:

> On Sunday, 18 December 2022 at 20:22:16 UTC, Roman P wrote:
>
>> 3) What happens when you overflow an int variable, that is, set
>> it to a value beyond its range?
>
> Undefined Behaviour.

In the normal case, and most likely what is being asked about,
not undefined behavior, but implementation-defined behavior, or
(from C99 on) raise an implementation-defined signal.

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#168604

On 12/18/2022 5:18 PM, Tim Rentsch wrote:
> Tony Oliver <guinness.tony@gmail.com> writes:
> 
>> On Sunday, 18 December 2022 at 20:22:16 UTC, Roman P wrote:
>>
>>> 3) What happens when you overflow an int variable, that is, set
>>> it to a value beyond its range?
>>
>> Undefined Behaviour.
> 
> In the normal case, and most likely what is being asked about,
> not undefined behavior, but implementation-defined behavior, or
> (from C99 on) raise an implementation-defined signal.
> 

Touche.

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#168648

On 12/18/22 13:18, Tony Oliver wrote:
> Signal SIGFPE is raised.

What happens to programs running on systems that don't support signals? :^)

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#168650

On Tuesday, 27 December 2022 at 11:22:37 UTC+2, Niles Rogoff wrote:
> On 12/18/22 13:18, Tony Oliver wrote: 
> > Signal SIGFPE is raised. 
> 
> What happens to programs running on systems that don't support signals? :^)

The nasal demons by standard. Or if the implementors were trying to be
nice (they sometimes try) then #include <signal.h> and using stuff from it
might give some diagnostics.

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#168664

Öö Tiib <ootiib@hot.ee> writes:
> On Tuesday, 27 December 2022 at 11:22:37 UTC+2, Niles Rogoff wrote:
>> On 12/18/22 13:18, Tony Oliver wrote: 
>> > Signal SIGFPE is raised. 
>> 
>> What happens to programs running on systems that don't support signals? :^)
>
> The nasal demons by standard. Or if the implementors were trying to be
> nice (they sometimes try) then #include <signal.h> and using stuff from it
> might give some diagnostics.

Nile snipped the context (probably making a joke).  The claim was that
integer division by 0 raises SIGFPE.  The standard doesn't say or imply
anything like that.  SIGFPE isn't even one of the 3 signals requires by
the standard.

Integer division by 0 is undefined behavior.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */

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#168651

On 12/27/22 04:22, Niles Rogoff wrote:
> On 12/18/22 13:18, Tony Oliver wrote:
>> Signal SIGFPE is raised.
> 
> What happens to programs running on systems that don't support signals? :^)

The only answer that fits all systems is that the behavior is undefined.
Singe the FP in SIGFPE stands for floating point, and the question was
about dividing an int value by 0, raising SIGFPE seems rather odd, but
it's certainly not prohibited.

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#168654

James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>On 12/27/22 04:22, Niles Rogoff wrote:
>> On 12/18/22 13:18, Tony Oliver wrote:
>>> Signal SIGFPE is raised.
>> 
>> What happens to programs running on systems that don't support signals? :^)
>
>The only answer that fits all systems is that the behavior is undefined.
>Singe the FP in SIGFPE stands for floating point, and the question was
>about dividing an int value by 0, raising SIGFPE seems rather odd, but
>it's certainly not prohibited.

Notwithstanding the "FP" in the name, SIGFPE isn't specific to floating
point.   

https://pubs.opengroup.org/onlinepubs/009695399/basedefs/signal.h.html


SIGFPE - Erroneous arithmetic operation.

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#168661

scott@slp53.sl.home (Scott Lurndal) writes:
>James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>>On 12/27/22 04:22, Niles Rogoff wrote:
>>> On 12/18/22 13:18, Tony Oliver wrote:
>>>> Signal SIGFPE is raised.
>>> 
>>> What happens to programs running on systems that don't support signals? :^)
>>
>>The only answer that fits all systems is that the behavior is undefined.
>>Singe the FP in SIGFPE stands for floating point, and the question was
>>about dividing an int value by 0, raising SIGFPE seems rather odd, but
>>it's certainly not prohibited.
>
>Notwithstanding the "FP" in the name, SIGFPE isn't specific to floating
>point.   
>
>https://pubs.opengroup.org/onlinepubs/009695399/basedefs/signal.h.html
>
>
>SIGFPE - Erroneous arithmetic operation.

The siginfo_t.si_code field encodes the actual error:

SIGFPE si_code mapping:
	FPE_INTDIV   Integer divide by zero.
        FPE_INTOVF   Integer overflow.
        FPE_FLTDIV   Floating-point divide by zero.
        FPE_FLTOVF   Floating-point overflow.
        FPE_FLTUND   Floating-point underflow.
        FPE_FLTRES   Floating-point inexact result.
        FPE_FLTINV   Invalid floating-point operation.
        FPE_FLTSUB   Subscript out of range.

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#168669

scott@slp53.sl.home (Scott Lurndal) writes:
> James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>>On 12/27/22 04:22, Niles Rogoff wrote:
>>> On 12/18/22 13:18, Tony Oliver wrote:
>>>> Signal SIGFPE is raised.
>>> 
>>> What happens to programs running on systems that don't support signals? :^)
>>
>>The only answer that fits all systems is that the behavior is undefined.
>>Singe the FP in SIGFPE stands for floating point, and the question was
>>about dividing an int value by 0, raising SIGFPE seems rather odd, but
>>it's certainly not prohibited.
>
> Notwithstanding the "FP" in the name, SIGFPE isn't specific to floating
> point.   
>
> https://pubs.opengroup.org/onlinepubs/009695399/basedefs/signal.h.html
>
>
> SIGFPE - Erroneous arithmetic operation.

True, but not particularly relevant.  It's true that on *some*
implementations, in some circumstances, integer division by 0 can result
in a SIGFPE (on my system, it does so at optimization levels 0 and 1,
and raises SIGILL at levels 2 and 3, with the simple example I tried).

But the question purported to be about the C language, which does not
define the behavior of integer division by zero.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */

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#168649

On 12/18/22 13:18, Tony Oliver wrote:
> Signal SIGFPE is raised.

What happens to programs running on systems that don't support signals? :^)

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#168655

Niles Rogoff <eternal-september@niles.xyz> writes:
>On 12/18/22 13:18, Tony Oliver wrote:
>> Signal SIGFPE is raised.
>
>What happens to programs running on systems that don't support signals? :^)

That's described in the documentation for that system.

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#168576

Roman P <invalid@example.com> writes:

I now see that this is cross-posted to comp.lang.c++ as well as to
comp.lang.c.  That's not a good idea for quizzes like this.

> 1) What happens when you divide an int variable by 0?

Asking what "happens" in this sort of context is a bit odd, but maybe
clarifying what this might mean is part of the question?

> 2) What happens when you divide a double variable by 0?
> 3) What happens when you overflow an int variable, that is, set it to a 
> value beyond its range?

And here there is even more ambiguity since a variable (what might
better be called a named object) can be set in two ways, and the C
standard says different things about each!

> 4) What is the difference between x = y++; and x = ++y;?
> 5) What is the difference between break, continue, and return when used 
> inside a loop statement?
> 6) What are the three parts of a for statement and which of them are 
> required?

The correct answer for C was made more complicated in 1999, and as for
C++, well that's a whole new ball game.

> 7) What is the difference between the = and == operators?
> 8) Does the following statement compile?
>
> for ( ; ; ) ;
>
> 9) What does the underscore _ represent in a switch expression?

There is no switch expression in C and a switch statement can include
lots of expressions.  But, that aside, I'd like to see what you think
the answer is.

> Merry Christmas to you all.

And to you too.

-- 
Ben.

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#168578

On Sun, 18 Dec 2022 21:22:32 +0000, Ben Bacarisse wrote:

> Roman P <invalid@example.com> writes:
> 
> I now see that this is cross-posted to comp.lang.c++ as well as to
> comp.lang.c.  That's not a good idea for quizzes like this.
[snip]
>> 9) What does the underscore _ represent in a switch expression?
> 
> There is no switch expression in C 

A quick google search brings up a page that addresses the OP's exact
question... in C# version 8. There, "The underscore (_) character 
replaces the default keyword to signify that it should match anything if 
reached." Perhaps the OP has confused C# with C and/or C++.

> and a switch statement can include lots of expressions.  But, that
> aside, I'd like to see what you think the answer is.

So would I.

Merry Winter Solstice, everyone. 
-- 
Lew Pitcher
"In Skills, We Trust"

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#168587

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

> Roman P <invalid@example.com> writes:
>
>> 3) What happens when you overflow an int variable, that is, set it
>> to a value beyond its range?
>
> And here there is even more ambiguity since a variable (what might
> better be called a named object) can be set in two ways, and the C
> standard says different things about each!

I don't know what you're getting at here.  ISTM that there is
basically only one way of setting a variable (or named object
if you will), in the sense that different ways of "setting a
variable" all reduce to the same semantics (not counting things
like memcpy(), unions, etc).  What am I missing?

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#168589

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:

> Roman P <invalid@example.com> writes:
>
>> 3) What happens when you overflow an int variable, that is, set
>> it to a value beyond its range?
>
> And here there is even more ambiguity since a variable (what might
> better be called a named object) can be set in two ways, and the C
> standard says different things about each!

Ahh, I may see what you're getting at here.  I was confused by
how you phrased it.

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#168577

On 12/18/2022 12:00 PM, Roman P wrote:
> 1) What happens when you divide an int variable by 0?
> 2) What happens when you divide a double variable by 0?
> 3) What happens when you overflow an int variable, that is, set it to a
> value beyond its range?
> 4) What is the difference between x = y++; and x = ++y;?
> 5) What is the difference between break, continue, and return when used
> inside a loop statement?
> 6) What are the three parts of a for statement and which of them are
> required?
> 7) What is the difference between the = and == operators?
> 8) Does the following statement compile?
> 
> for ( ; ; ) ;
> 
> 9) What does the underscore _ represent in a switch expression?
> 

Do your own homework.

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#168579

On 12/18/2022 12:00 PM, Roman P wrote:
> 1) What happens when you divide an int variable by 0?
[...]

Undefined behavior.

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