More compiler oddities

BradC

Just for the record.
You don't need to declare a CON block.
Starting the file with..
FRED = 24, A = 1, B = 2
.. works perfectly..

You don't need to declare your enumerators from zero.. it happens by default in the con block..
so
CON A, B, C
za = 24, zb = 25
D, E, F

will give you A = 0, B = 1, C = 2, D = 3... and so on..

You can space your enumerators..
#0, A[noparse][[/noparse]10], B[noparse][[/noparse]10], C[noparse][[/noparse]10]
will give you A = 0, B = 10, C = 20..
And you can use pre-defined constants and mathematics in the [noparse]/noparse fields..
so
zz = 20
A[noparse][[/noparse]zz], B[noparse][[/noparse]zz+10], C[noparse][[/noparse]zz]
will give you A = 0, B = 20, C = 50..

You never know when it might come in handy [noparse]:)[/noparse]

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Pull my finger!

Phil Pilgrim (PhiPi)

Interesting discovery! Odd that it's not in the manual, since it could be rather useful.

Using that technique, here's an easy way to express a Fibonacci sequence using CON:

[b]CON[/b]

  [b]_clkmode[/b]      = [b]xtal[/b]1 + [b]pll[/b]16x
  [b]_xinfreq[/b]      = 5_000_000

  #1, a[noparse][[/noparse]0], b[noparse][[/noparse]a], c[noparse][[/noparse]b], d[noparse][[/noparse]c], e[noparse][[/noparse]d], f[noparse][[/noparse]e], g[noparse][[/noparse]f]

[b]OBJ[/b]

  pr : "tv_wtext"

[b]PUB[/b] Start | i

  pr.start(12)
  pr.dec(a)
  pr.out(" ")
  pr.dec(b)
  pr.out(" ")
  pr.dec(c)
  pr.out(" ")
  pr.dec(d)
  pr.out(" ")
  pr.dec(e)
  pr.out(" ")
  pr.dec(f)
  pr.out(" ")
  pr.dec(g)

-Phil

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'Still some PropSTICK Kit bare PCBs left!

Rayman

Interesting! Maybe this should go in Tricks&Traps (if not already there...).

BradC

I suspect its an oddity related to consolidating the way VAR and CON blocks are parsed, so its not in the manual as it was probably not an intended language feature, but maybe shared code in the tokenizer/lexer/parser..

It certainly has the potential to be useful anyway..
Another "interesting" point is the [noparse]/noparse block does not need to be attached to its parent. Whitespace is gracefully ignored.

ie
CON
A [noparse][[/noparse]10] , B [noparse][[/noparse]10]
VAR
long Fred [noparse][[/noparse]15]

are all perfectly valid.. it makes it easier when looking at it from the perspective of a tokenizer..

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Pull my finger!

Phil Pilgrim (PhiPi)

'Makes sense. CONstants are treated like the addresses of phantom byte arrays, which can be assigned either explicitly (x = n) or implicitly (#n being like an ORG).

-Phil

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'Still some PropSTICK Kit bare PCBs left!

heater

Hmm, I stumbled across these oddities a few weeks ago. Thought everyone knew so I kept quite.

Phil: I love that fibo sequence idea.

"Makes sense" In a kind of Alice in Wonderland way. Strangest syntax for enums I ever saw.

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For me, the past is not over yet.

Ariba

From the sourcecode of the VGA HiRes Text Driver:

...
CON
  #1, scanbuff[noparse][[/noparse]128], scancode[noparse][[/noparse]128*2-1+3], maincode      'enumerate COG RAM usage
...

So this enumeration syntax seems to be expected, but not documented in the Manual.

Andy