uninitialised structs,

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lazer1

Joined: 24 Jan 2006
Posts: 185

lazer1 16 Feb 2006, 01:24

I want to do the following:

Code:

struc point x,y
   {
   .x  db x
   .y  db y
   }

so that I can do:

Code:

varxy   point  1,2
varz   point

where in the second case I want all fields initialised to 0,

now the only way I have found to do this is:

Code:

struc point x,y
   {
   if x eq
      .x  db 0
   else
      .x  db x
   end if

   if y eq
      .y db 0
   else
      .y db y
   end if
   }

but this is quite complicated,
is there a simpler way to do this? Razz

I tried using a macro:

Code:

macro  field x,dz
    {
    if x eq
       .#x  dz 0
    else
       .#x  dz x
    end if
    }

struc  point x,y
   {
   field x,db
   field y,db
   }

but fasm didnt accept this Sad

, not sure why,

16 Feb 2006, 01:24

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8354
Location: Kraków, Poland

Tomasz Grysztar 16 Feb 2006, 10:05

The good old trick for doing this is:

Code:

struc point x,y
   {
   .x  db x+0
   .y  db y+0
   }

As for your solution, it didn't work because you used value as if it was the name also. You should do it like:

Code:

macro  field n,dz,v
    {
    if v eq
       n dz 0
    else
       n dz v
    end if
    }

struc  point x,y
   {
   field .x,db,x
   field .y,db,y
   }

or maybe:

Code:

struc Db v
{ if v eq
   . db 0
  else
   . db v
  end if }

struc point x,y
   {
   .x  Db x
   .y  Db y
   }

16 Feb 2006, 10:05

dead_body

Joined: 21 Sep 2005
Posts: 187
Location: Ukraine,Kharkov

dead_body 16 Feb 2006, 10:06

maybe something like this, but I don't know will it work:
struc point x,y
{
.x db x+0
.y db y+0
}
sorry if it would not work.

16 Feb 2006, 10:06

lazer1

Joined: 24 Jan 2006
Posts: 185

lazer1 16 Feb 2006, 12:52

Tomasz Grysztar wrote:

The good old trick for doing this is:

Code:

struc point x,y
   {
   .x  db x+0
   .y  db y+0
   }

this trick looks really neat Razz

the other 2 will be useful for understanding how fasm operates,

the 3rd technique with the "." is very unusual,
I havent yet fully understood this one:

say I have:

Code:

xyz   point  3

after the first expansion of point will this be translated to:

Code:

xyz
    .x Db 3
    .y Db

and then after the second expansion of Db to:

Code:

xyz 
    .x
    . db 3
    .y
    . db 0

16 Feb 2006, 12:52

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 16 Feb 2006, 13:16

nope, after usage of "a point 5,6" it becomes

Code:

a.x Db 5 
a.y Db 6

eg. structure name ("a") is prepended to all symbols starting with dot (".x" and ".y"), and macro arguments are replaced by theior values ("x" -> 5, "y" ->6)

Then also inner macros ("Db") are expanded, "a.x Db 5" becomes

Code:

if 5 eq 
 a.x db 0 
else 
 a.x db 5
end if }

eg. "." is replaced with structure name "a.x", and "v" is replaced by it's value "5". Rest is not preprocessing... "if 5 eq " is false condition so "a.x db 5" gets assembled. In case of empty argument condition would be "if eq" which is true, so "a.x db 0" would be assembled

16 Feb 2006, 13:16

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