global constant ?

Chris Micro · 2009-05-18 07:16

Hi there,

is it possible in SPIN to create global constants which are available in every object in a project?
In "C" there are the header files: you can define gobal constants there and include the header file in every code file.

Is the same thing possible in SPIN?

thanx,
chris

RossH · 2009-05-18 07:32

Hi Chris,

You can do something similar by declaring constants in one SPIN file, then referring to them in another file using the "#" syntax. For example:

In file "MY_CONSTANTS.SPIN":

CON
CONST_1 = 1
CONST_2 = 2

PUB Dummy

Then, to use these constants in another file:

OBJ
MY_CONSTANTS : "MY_CONSTANTS.SPIN"

CON
X = MY_CONSTANTS#CONST_1

PUB
...

This approach has a few drawbacks - for instance, each constant file you have actually consumes some memory. But it may be useful to you.

Ross.

Chris Micro · 2009-05-18 08:34

Hmm, I'm not shure if that helps realiy.

What I want to have is a file with the hardware ports definitions e.g.

VGA_PINS = 16
...

Of course the hardware connections are for every object the same and therefore it should be possible to have a global pin definition file.

RossH · 2009-05-18 08:50

Hi Chris,

There have been various attempts to come up with a solution to this exact problem. I don't think any of them are ideal. The issue (as you have discovered) is that basic support for this needs to be built into the language in the first place. Various people have tried "bolt on" solutions to overcome the shortcomings of SPIN - but (again) I'm not aware of any having achieved resounding success. They tend to be either non-standard extensions to the SPIN language, or require the use of a SPIN pre-processor.

Try searching the forum for various language tools - you could start with bstc, Homespun and SCUM.

Or you could just use C - see http://forums.parallax.com/showthread.php?p=795326

Ross.

Ale · 2009-05-18 08:56

My programs are just one big file, so all my constants are global

. No "objects", almost no SPIN, just asm. Pure, fast, nice, spaghetti-shaped pasm

You should look at the compiled code, I do not think you consume that much memory, the problem is you need at least one PUB per spin file, but that one can be just one abort, break or repeat command, one byte (2 really)and few pointers. It will use 10 bytes. With BST you can remove unused methods

, and save juicy 2 bytes !!!

test2.spin

VAR

  byte a, b, c

OBJ
  consts : "consts"


PUB start

  a := b + consts#const1 * consts#const2

consts.spin

CON
  const1 = 500
  const2 = 600

PUB nada
  abort

|===========================================================================|
Objects : -
test2
  |
  +--consts

Object Address : 0010 : Object Name : test2
Object Address : 002C : Object Name : consts

Binary Image Information :
PBASE : 0010
VBASE : 0038
DBASE : 0044
PCURR : 001C
DCURR : 0048
|===========================================================================|
|===========================================================================|
Object test2
Object Base is 0010
|===========================================================================|
Object Constants
|===========================================================================|
|===========================================================================|
|===========================================================================|
VBASE Global Variables
|===========================================================================|
VBASE : 0000 BYTE Size 0001 Variable a
VBASE : 0001 BYTE Size 0001 Variable b
VBASE : 0002 BYTE Size 0001 Variable c
|===========================================================================|
|===========================================================================|
Spin Block start with 0 Parameters and 0 Extra Stack Longs. Method 1
PUB start

Local Parameter DBASE:0000 - Result
|===========================================================================|
11                        a := b + consts#const1 * consts#const2
Addr : 001C:          88 01  : Memory Op Byte VBASE + READ Address = 0001
Addr : 001E:       39 01 F4  : Constant 2 Bytes - 01 F4 
Addr : 0021:       39 02 58  : Constant 2 Bytes - 02 58 
Addr : 0024:             F4  : Math Op *     
Addr : 0025:             EC  : Math Op +     
Addr : 0026:          89 00  : Memory Op Byte VBASE + WRITE Address = 0000
Addr : 0028:             32  : Return        
|===========================================================================|
Object consts
Object Base is 002C
|===========================================================================|
Object Constants
|===========================================================================|
|===========================================================================|
Spin Block nada with 0 Parameters and 0 Extra Stack Longs. Method 1
PUB nada

Local Parameter DBASE:0000 - Result
|===========================================================================|
6                        abort
Addr : 0034:             30  : Abort         
Addr : 0035: Data : 32                       2

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Visit the home of pPropQL, pPropQL020 and OMU for the pPropQL/020 at omnibus.uni-freiburg.de/~rp92

Chris Micro · 2009-05-18 12:26

Hi Ale,

I know, assembler is best

But as you know, I like to learn also SPIN, even it's sometime a little bit odd ....

Hi RossH,

thanx for your help

Very pitty that it is not possible with spin, so I have to copy the global constant block in every object .-(

Ale · 2009-05-18 15:03

Chris: As I demonstrated before, you can use RossH idea losing only 10 bytes in the process.

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Visit the home of pPropQL, pPropQL020 and OMU for the pPropQL/020 at omnibus.uni-freiburg.de/~rp92

jazzed · 2009-05-18 18:20

Chris Micro said...

thanx for your help Very pitty that it is not possible with spin, so I have to copy the global constant block in every object .-(

The C preprocessor is including that global const block for you.
Don't Homespun and BSTC both have a preprocessor?
No preprocessor is of course a glaring missed opportunity in the Propeller tool [noparse]:)[/noparse]

Chris Micro said...

In "C" there are the header files: you can define gobal constants there and include the header file in every code file.

There is not much difference in '#include <const.h>' to get #defines/enum and 'OBJ con : "const.spin" '
except of course that you add con# to each symbol ... which has many advantages over #defines, etc....

Enjoy!

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--Steve

Propalyzer: Propeller PC Logic Analyzer
http://forums.parallax.com/showthread.php?p=788230

BradC · 2009-05-18 22:39

jazzed said...

Don't Homespun and BSTC both have a preprocessor?

Not that can include files.. only conditional compilation.

jazzed said...

No preprocessor is of course a glaring missed opportunity in the Propeller tool [noparse]:)[/noparse]

You just can't be all things to all people.

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"VOOM"?!? Mate, this bird wouldn't "voom" if you put four million volts through it! 'E's bleedin' demised!

global constant ?

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