Match directive and lazy evaluation

Ability of match to replace the symbolic constants with their values has interesting side effect:

Code:

; Simple macros to display symbolic constants
macro s_display symbol* { display `symbol }
macro v_display symbol* { match vv,symbol \{ irps v,vv \\{ s_display v \\} \} }
macro sv_display [symbol] {
  s_display symbol
  display "="
  v_display symbol
  display 13, 10
}
; Here goes the magic (equ's are placed backward intentionally)
thousand equ ten*hundred
hundred equ ten*ten
ten equ 10
sv_display thousand, hundred, ten
match vv,thousand { match v,vv \{ dd v \} }
match v,hundred { dd v }

Display: wrote:

thousand=ten*hundred
hundred=ten*ten
ten=10

Plain dd thousand or hundred both fail, as you may have guessed.
It appears that match does replacement only once, so we have to peel that thousand onion twice.

May equ be of some help?

Code:

; Append to the previous code
real_thousand equ thousand
sv_display real_thousand
really_real_thousand equ real_thousand
sv_display really_real_thousand

Display: wrote:

real_thousand=ten*hundred
really_real_thousand=ten*hundred

Bad luck. Let's tweak it more:

Code:

; Append to the previous code
; Simple evaluating equ (1.69.00+)
struc equ! expr* { rept 1 v:expr \{ . equ v \} }
match vv,thousand { match v,vv \{ real_thousand equ! v \} }
sv_display ten, real_thousand
; For something different
ten equ ten*ten
match vv,thousand { match v,vv \{ real_thousand equ! v \} }
sv_display ten, real_thousand

Display: wrote:

ten=10
real_thousand=1000
ten=10*10
real_thousand=1000000

Quite amusing. Deferred symbolic constant replacement may be useful. The next result astounds me.

Code:

; Append to the previous code
; That was predictable, how about this?
ten equ 10+10
match vv,thousand {;step by step
  display "Step 1: vv="
  v_display vv
  display 13, 10
  match v,vv \{
    display "Step 2: v="
    v_display v
    dd v; output file contains 220
    display 13, 10
    WTF?! equ! v
  \}
}
sv_display ten, WTF?!

Display: wrote:

Step 1: vv=10+10*ten*ten
Step 2: v=10+10*10+10*10+10
ten=10+10
WTF?!=4010

How it could be possible? Probably equ! is responsible for that…

Code:

; Append to the previous code
; Test the evaluator
result equ! 10+10*10+10*10+10
sv_display result

Display: wrote:

result=220

Hmm, I'm lost. Looks like equ! calculates 10+10*(10+10)*(10+10) when invoked within match. Remains of token boundaries?

Code:

; Append to the previous code
; Test the hypothesis
match v,hundred { WTF?! equ! v }
sv_display ten, WTF?!

Display: wrote:

ten=10+10
WTF?!=400

Aha! Now it becomes clearer. Let's add another match to get it right.

Code:

; Append to the previous code
; Test the hypothesis II
match vv,hundred { match v,vv \{ good_one equ! v \} }
sv_display ten, good_one

Display: wrote:

ten=10+10
good_one=120

Perfect match! Wink

Disclaimer:
Those macros are limited in functionality, don't expect too much from them.
FASM macro programming is highly addictive and can be dangerous to your mental health.