Comments on: Getting Along With The Comma Operator in C++ https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/ Jonathan Boccara's blog Sun, 19 Aug 2018 10:42:00 +0000 hourly 1 https://wordpress.org/?v=6.5.3 By: MPM https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1233 Sun, 19 Aug 2018 10:42:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1233 In reply to Uri Goren.

Good point! That might have been what the engineer did.

]]> By: Uri Goren https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1222 Wed, 15 Aug 2018 13:06:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1222 In reply to MPM.

Maybe the infinite loop was found and “fixed”:
while (x > (999,999));

]]> By: Jonathan Boccara https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1205 Sun, 05 Aug 2018 09:11:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1205 In reply to MPM.

Awesome story, thanks for sharing 🙂

]]> By: pepper_chico https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1198 Wed, 01 Aug 2018 00:35:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1198 I have some special usages in my blog http://nosubstance.me/post/cpp-unnamed-programming-addendum/

]]> By: Martin Moene https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1197 Tue, 31 Jul 2018 19:54:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1197 Colllect bits for a register mask in embedded programming, like:

// register adcsra:
set( prescale::factor::x128 )
, set( enable::adc::on )
, set( enable::interrupt::on )
, set( enable::auto_trigger::on )
, conversion::start()
;

See Combine lazy writes via comma operator:

https://github.com/martinmoene/kalman-estimator/blob/01fae7efaaf317e1a00b776608805c929313246e/include/mcu/register.hpp#L346

]]> By: Piotr Obst https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1196 Tue, 31 Jul 2018 19:21:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1196 In reply to MPM.

Yes I got that, it is funny actually. But just wanted to point that out so that someone doesn’t get confused.

]]> By: MPM https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1195 Tue, 31 Jul 2018 19:18:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1195 In reply to Piotr Obst.

Ah yes, that’s correct, because of operator precedence. I couldn’t remember the exact code or the exact behavior, but the point I was trying to make is that the engineer was writing integer literals with commas, and it compiled fine but did something completely unexpected.

]]> By: Piotr Obst https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1194 Tue, 31 Jul 2018 19:09:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1194 In reply to MPM.

Nah, it is equivalent of while(999) which is while(1) so it is infinite loop.

—

I also think that this is a very good article.

]]> By: Lưu Vĩnh Phúc https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1191 Tue, 31 Jul 2018 11:33:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1191 Boost has overloaded the comma operator for good long before C++17

vector v;
v += 1,2,3,4,5,6,7,8,9;

There are some other practical examples here https://stackoverflow.com/q/5602112/995714

]]> By: jft https://www.fluentcpp.com/2018/07/31/how-to-get-along-with-the-comma-operator/#comment-1190 Tue, 31 Jul 2018 09:54:00 +0000 https://www.fluentcpp.com/?p=1487#comment-1190 Oh the fun that can be had with , ! This is one of my favourites

int a = 1;
int b = 1;
bool c = true;

c ? ++a, ++b : –a, –b;

cout << a << " " << b << endl;

if anyone says that the output is 2 2 step away from the keyboard now! Look further down for the answer

c ? ++a, ++b : –a, –b;

is actually parsed as

(c ? ++a, ++b : –a), –b;
because , has the lowest operator precedence and the , following –a therefore terminates the ternary !

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