Strange Assignment Statement? 1

[Borvik]

Hello all,

I'm relatively new to C++ (I know enough to read it, and code a little bit), but I'm stumped on a line of code I'm reading.

I'm trying to convert a part of a C++ program to PHP and just don't know what the heck the C++ means. Here's the C++ (a and val are variables):

( a += (val + e),  a = a << val | a >> (5 - val),  a += val )

I get the left/right shift and all that, but I haven't seen an assignment statement (I'm assuming it's an assignment) that looks like that before.

Thanks.

 

[cpjust]

It looks like 3 assignment statements to me:

a += (val + e);
a = a << val | a >> (5 - val);
a += val;

a += val means: a = a + val

That middle monster is pretty scary... I think they should fire the guy that wrote it.
I believe it is equivalent to this (assuming a is an int):

int a1 = a << val;
int a2 = a >> (5 - val);
a = a1 | a2;

The | is just ORing the two values together.

 

[Borvik]

The original statement was in a define call with parameters so that it could be replaced elsewhere:

#define my_func(a, val, e) ( a += (val + e),  a = a << val | a >> (5 - val),  a += val )

So it's possible the statement might look more like this:

a += (val + e),  a = a << val | a >> (5 - val),  a += val;

 

[Borvik]

Ah, so the commas just mean multiple assignments then?!

 

[cpjust]

Yes, it's a relic of lazy C assignments like:

int i, j, k;

http://msdn2.microsoft.com/en-us/library/zs06xbxh.aspx