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/

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);	
}

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`.