• Jim (33/33) Nov 08 2016 Hi,
• rikki cattermole (13/46) Nov 08 2016 This is a set of syntax that isn't ugh used often (I'm pretty sure I
• ketmar (2/3) Nov 08 2016 `.a` --> `::a`.

Jim <jhyslop dreampossible.ca> writes:

Hi,

I'm a very experienced C++ programmer, looking at a program 
written in D. D is similar enough to C++ and Java that I have no 
problem understanding it - except for one thing. I think I may 
have figured it out, but I want to confirm my understanding.

What does it mean when a variable name starts with a '.'

Here's an extract from the code:
/// move.d ////////////
module move;

import empire;
import eplayer;
import sub2;

[...]

void updlst(loc_t loc,int type)		// update map value at loc
{
    int ty = .typ[.map[loc]];		// what's there

... etc.
(loc_t is an alias for int)

Would the equivalent in C or C++ be:

typedef int loc_t;
extern int typ[];
extern int map[];
void updlst( loc_t loc, int type )
{
    int ty = typ[map[loc]];

/////// var.d  ////////////////////////////////
module var;
import empire;
import eplayer;

int typ[MAPMAX] = ...etc...
ubyte map[MAPSIZE] = [0,];	// reference map

If you need more context, the complete source code is available 
from http://www.classicempire.com/

rikki cattermole <rikki cattermole.co.nz> writes:

On 09/11/2016 7:28 PM, Jim wrote:
 Hi,

 I'm a very experienced C++ programmer, looking at a program written in
 D. D is similar enough to C++ and Java that I have no problem
 understanding it - except for one thing. I think I may have figured it
 out, but I want to confirm my understanding.

 What does it mean when a variable name starts with a '.'

 Here's an extract from the code:
 /// move.d ////////////
 module move;

 import empire;
 import eplayer;
 import sub2;

 [...]

 void updlst(loc_t loc,int type)        // update map value at loc
 {
    int ty = .typ[.map[loc]];        // what's there

 ... etc.
 (loc_t is an alias for int)

 Would the equivalent in C or C++ be:

 typedef int loc_t;
 extern int typ[];
 extern int map[];
 void updlst( loc_t loc, int type )
 {
    int ty = typ[map[loc]];

 /////// var.d  ////////////////////////////////
 module var;
 import empire;
 import eplayer;

 int typ[MAPMAX] = ...etc...
 ubyte map[MAPSIZE] = [0,];    // reference map

 If you need more context, the complete source code is available from
 http://www.classicempire.com/

This is a set of syntax that isn't ugh used often (I'm pretty sure I 
know what it is). It just isn't needed.

Empire's code was ported to D during the early days of D1, its 
documentation doesn't come close to best practices let alone the code 
itself.

Example:

int x;

void main() {
	x = 8;

	import std.stdio;
	writeln(.x);	
}

ketmar <ketmar ketmar.no-ip.org> writes:

On Wednesday, 9 November 2016 at 06:28:31 UTC, Jim wrote:
 What does it mean when a variable name starts with a '.'

`.a` --> `::a`.