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entropy: sorta under the 128 byte level

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This commit is contained in:
Vince Weaver 2018-05-28 01:12:32 -04:00
parent 3b64e895c3
commit 09c3e7d70b
1 changed files with 10 additions and 13 deletions
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23
two-liners/entropy.s
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@ -20,6 +20,8 @@
; 139 bytes: change jmp to bcs
; 138 bytes: jmp at end now fits into a bcs
; 136 bytes: store YPOS on stack
; 135 bytes: store X to HGR_SCALE rather than TXA+STA
; 131 bytes: some fancy branch elimination by noticing X=1
;BLT=BCC, BGE=BCS
@ -112,24 +114,20 @@ xloop:
; Compare to E
jsr MUL10 ; EPOS is *100, so multiply*100 first
jsr MUL10
jsr MUL10
jsr CONINT
; X is now RND(1)*100
jsr CONINT ; convert to int
; X is now RND(1)*100
cpx EPOS
bcc less ; branch if less than EPOS
more:
lda #1 ; the boring case
bne done ; branch always
less:
ldx #1 ; the boring case
bcs done ; branch if less than EPOS
; SCALE=RND(1)*E*20+1
; EPOS is E*100, so RND(1)*(EPOS/10)*2+1
; is EPOS/4 close enough?
; put random value in FAC
ldx #1 ; RND(1), Force 1
; ldx #1 ; RND(1), Force 1
jsr RND+6 ; we skip passing the argument
; in FAC as that would be a pain
@ -147,10 +145,9 @@ less:
jsr CONINT ; convert to int (in X)
inx ; add 1
txa ; move to A
done:
sta HGR_SCALE ; set scale value
stx HGR_SCALE ; set scale value
ldy XPOSH ; setup X and Y co-ords
ldx XPOS