Conditional symbol definitions

[Thomas Jentzsch]

Instead of doing this ...

  IF SWITCH = 0
SYMBOL = 7
  ENDIF
  IF SWITCH = 1
SYMBOL = 10
  ENDIF
  IF SWITCH = 2
SYMBOL = 15
  ENDIF

... I am looking for an easier way. Something like ...

ARRAY = 7, 10, 15
SYMBOL = ARRAY[SWITCH]

would be nice.

 

Is there something like this existing in DASM?

[+Andrew Davie]

Mmh. How about using operators?

Works for a small # symbols.

SWITCH = 0   ; or 1 or 2
ARRAY = $0F0A07
SYMBOL = ((ARRAY >> (8*SWITCH)) & $FF

It works up to the size of numbers held by dasm.

Perhaps, though, you could extend this by using the string functions

Not quite sure how they work though

 

 

Edited April 12, 2021 by Andrew Davie

[Thomas Jentzsch]

Interesting approach. Thanks!

 

Now we only need something for a large number of symbol variations.  

[+Andrew Davie]

You can change it so the shift = next power of 2 up from maximum # symbols.

And then you can squash lots more in.

For the given example, 0/1/2, then we need 2 bits, so the shift is 2.

Building the array is a bit trickier...

 

ARRAY = (SYM1<<4)|(SYM2<<2)|(SYM3<<0)
... where SYM1..SYM3 are values in the range 0..2

 

 

 

 

[Thomas Jentzsch]

While this works, it is IMO pretty odd and not easy to understand especially later on. 

[Thomas Jentzsch]

19 hours ago, Andrew Davie said:

It works up to the size of numbers held by dasm.

Unfortunately 32 bit is the limit here.

 

If expressions would all access to generated code, one could create tables in uninitialized segments and read from these. 

Edited April 13, 2021 by Thomas Jentzsch