e-LMC extended Little Man Computer bubble embedded program continuous input

问题

I am looking for a e-LMC extended little man computer program that will accept an indefinite inputs and bubble-sort them. I need to have more inputs continuous and then do the bubble sort.

INP //read 1st value
STA 0 // for store
INP // read 2nd value
   STA 1 // store
INP // read 3rd value
STA 2 // store
LDA 1 // LOOP 1, STEP 1:
    SUB 0 //
BRP STEP2 // if R0 and R1 are in order, don't swap them
LDA 1 // Begin swapping registers
STA 3   
LDA 0
STA 1 // R1 = R0
LDA 3
STA 0 //R0 = temp
STEP2 LDA 2 // LOOP 1, STEP 2
SUB 1
BRP STEP3 // If R1 and R2 are in order, don't swap them
LDA 2 // Begin swapping registers
STA 3 // temp =R2
LDA 1
STA 2 //R2=R1
   LDA 3
STA 1 // R1 = temp
STEP3 LDA 1 // LOOP 2, STEP 1
SUB 0
BRP STEP4 // if R0 andR1 are in order, don't swap them
LDA 1 // Begin swapping registers
STA 3 // temp = R1
LDA 0
STA 1 //R1=R0
LDA 3
STO 0 // R0 = temp

STEP4 LDA 0
OUT
   LDA 1
   OUT
LDA 2
OUT
   HLT

回答1:

As I am not familiar with e-LMC, I provide here a pure LMC implementation. The downside is of course that space is limited with an LMC. As the below code occupies 62 mailboxes excluding the input array, a maximum of 38 values can be input (this is not verified).

I opted to mark the end of the input with a terminating 0 value, i.e. the values to be sorted cannot include 0.

As you already indicated in comments, this solution relies heavily on self-modifying code. All instructions that are labelled with get***, set*** and cmp*** are dynamically changed to point to the right element in the array.

You can run this code in this snippet (it loads an emulator):

#input: 5 2 4 1 3 0
         LDA setfirst
         STA setcurr1
input    INP
setcurr1 STA array
         BRZ isempty
         LDA setcurr1
         ADD one
         STA setcurr1
         BRA input

isempty  LDA array
         BRZ zero     ; empty array
sort     LDA getfirst ; init "curr" indices
         STA getcurr1
         STA getcurr2
         LDA setfirst
         STA setcurr2
         LDA cmpfirst
         STA cmpcurr
         STA issorted ; bool: assume sorted

loop     LDA getcurr1 ; set "next" indices
         ADD one
         STA getnext1
         STA getnext2
         LDA setcurr2
         ADD one
         STA setnext

getnext1 LDA array
         BRZ check    ; end of array
cmpcurr  SUB array
         BRP inc      ; no swap needed
getcurr1 LDA array    ; swap
         STA temp
getnext2 LDA array
setcurr2 STA array
         LDA temp
setnext  STA array
         LDA zero
         STA issorted ; was not sorted yet
inc      LDA getnext1  ; increment "cur" indices
         STA getcurr1
         LDA setnext
         STA setcurr2
         LDA cmpcurr
         ADD one
         STA cmpcurr
         BRA loop

check    LDA issorted
         BRZ sort

getcurr2 LDA array
         BRZ zero     ; all done
         OUT
         LDA getcurr2
         ADD one
         STA getcurr2
         BRA getcurr2

; constants:
zero     HLT
one      DAT 1        
getfirst LDA array
setfirst STA array
cmpfirst SUB array

; variables:
issorted DAT ; boolean
temp     DAT ; for swapping
array    DAT ; start of array

<script src="https://cdn.jsdelivr.net/gh/trincot/lmc@v0.77/lmc.js"></script>

As you wrote that the e-LMC is an extension to the LMC, having more registers and addressing methods, I suppose it is not so hard to change this into a program that would take benefit of those extensions.

来源：https://stackoverflow.com/questions/64527608/e-lmc-extended-little-man-computer-bubble-embedded-program-continuous-input

标签

memory

bubble-sort

continuous

little-man-computer