evaluation order of parameters

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

Can I rely on the evaluation order of a function's parameters ? will the parameters of any function (make16 in this case) evaluate always left to right ? Example:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

When I saw your code, my first thought was "I would never do this".

But to provide documentation, here is one answer:
http://www.scit.wlv.ac.uk/cbook/chap3.order.html

Here is a large discussion on order of evaluation. It's not about
function parameters. It's about arithmetic evaluation, but it's still
useful. Scroll down about half way, to the example with two getc() statements in one line.
http://c-faq.com/~scs/readings/precvsooe.960725.html

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

I was just tempted to spare a temporary variable, not realizing, that the compiler allocates one anyway (?)
Although it worked as expected, I felt it is a bad practice, and you affirmed that. Thanks.

There's another (not evaluation-order-prone) dilemma: is it a good practice to squeeze as many intructions, operators as possible into one line (making a harder to read code), like

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

Thank you all. Regarding the first problem, I've come to this:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

In this case, a union of a 'long' and a struct (of two bytes) would be
considered better style. The reasons would be:

1. Better portability, in case you move to another compiler.

2. If someone else has to maintain your code in the future, it's easier
for them to understand if you use coding methods that are part of
standard C.