How can I complete this mmix code to calculate Factorial?

Question

I'm new in using mmix editor (we have to use it in the University) and now we have to complete this code to get the Factorial of the input , so the code is

                LOC     Data_Segment
                GREG    @
RESULT          OCTA    0
INPUT           OCTA    13

                LOC     #100
result          IS      $0
input           IS      $1

Main            LDO     input,INPUT
                PUSHJ   result,Factorial
                STO     result,RESULT
End             TRAP    0,Halt,0

                PREFIX  :Factorial:
inout           IS      $0
                [...]
:Factorial      [...]
End             POP     1,0

we have to complete just the [...] but it doesn't work . So I had to make some edites to get the right answer like this :

                LOC     Data_Segment
                GREG    @
RESULT          OCTA    0
INPUT           OCTA    13

                LOC     #100
result          IS      $0
input           IS      $1
count           IS      $2
Main            LDO     input,INPUT
                LDO     count,INPUT
                SET     result+1,input
                SET     result+2,count
                PUSHJ   result,Factorial
                STO     result,RESULT
End             TRAP    0,Halt,0

                PREFIX  :Factorial:
inout           IS      $0
count           IS      $1
test            IS      $2      
:Factorial      SUB     count,count,1
                MUL     inout,inout,count
                CMP     test,count,1
                BZ      test,End
                JMP     :Factorial
End             POP     1,0

Now the next step is to use Sub-routine instead of the (MUL inout,inout,count) . And here what I did :

                LOC     Data_Segment
                GREG    @
RESULT          OCTA    0
INPUT           OCTA    5

                LOC     #100
result          IS      $0
input           IS      $1
count           IS      $2
Main            LDO     input,INPUT
                LDO     count,INPUT
                SET     result+1,input
                SET     result+2,count
                PUSHJ   result,Factorial
                STO     result,RESULT
End             TRAP    0,Halt,0

                PREFIX  :Factorial:
inout           IS      $0
count           IS      $1
test            IS      $3      
:Factorial      SET     inout+1,inout
                SET     count+1,count
                PUSHJ   inout,:Multiply
                STO     inout,inout
                CMP     test,count,1
                BZ      test,End
                JMP     :Factorial
End             POP     1,0

                PREFIX  :Multiply:
inout2          IS      $0
count2          IS      $1
test2           IS      $3  
:Multiply       SUB     count2,count2,1
                ADD     inout2,inout2,inout2
                CMP     test2,count2,3              
                BZ      test2,EndMul
                JMP     :Multiply
EndMul          POP     1,0

But it gives me an infinite loop (because of the count variable).

How can I solve this?

Answer 1

:Factorial SET count,inout x SUB count,count,1 MUL inout,inout,count CMP test,count,1 BZ test,End JMP x End POP 1,0

try this for the first one ;)