Finding a prime

[timur77]

Program - decompositions into prime factors and finding a prime number


[m0]

input "Введите положительное, целое число, больше 1:";a1

if a1<2 then goto [m0]

a=a1

[m1]

b=int(a/2)

c=a-b*2

if c=0 Then print b;"|2":a=b:goto [m1]

[m2]

b=int(a/3)

c=a-b*3

if c=0 Then print b;"|3":a=b:goto [m2]

[m3]

b=int(a/5)

c=a-b*5

if c=0 Then print b;"|5":a=b:goto [m3]

i=7

aa=sqr(a)

[m5]

if i>aa then goto [m6]

   for e=0 to 6 step 2

       [m4]

       i1=i+e

       if (a mod i1)=0 Then print a/i1;"|";i1: a=a/i1: aa=sqr(a): goto [m4]

   next e

i=i+10

goto [m5]

[m6]

if a=a1 or a1=2 or a1=3 or a1=5 then print a1;"-простое"

goto [m0]



[svajoklis]

О, вы из Росии? Извините, мой Руский язик не очен хорошый))

To translate: oh, you are from Russia? Sorry, my russian is not very good

Anywho, I tried to work on your program a bit. A few more lines, but imho much more readable. Interesting algorithm!


   while 1
       input "Enter a whole number bigger than 1 (-1 to exit): "; number

       if number = -1 then exit while

       if int(number) = number and number > 1 then
           call doNumber number
       else
           print "Bad number, try again!"
       end if
   wend

   end

   ' divide number until a prime is reached
   ' print intermediate divisions
   sub doNumber number
       initialNumber = number
       knownPrime = 0

       if (initialNumber = 2) or _
          (initialNumber = 3) or _
          (initialNumber = 5) then knownPrime = 1

       ' haven't figured out if prime or not yet
       if knownPrime = 0 then

           call divideWhilePossibleBy number, 2
           call divideWhilePossibleBy number, 3
           call divideWhilePossibleBy number, 5

           i = 7
           numberSquared = sqr(number)

           while i <= numberSquared
               for e = 0 to 6 step 2
                   while 1
                       i1 = i + e
                       if number mod i1 <> 0 then exit while
                       call printDivision number, i1
                       number = number / i1
                       numberSquared = sqr(number)
                   wend
               next e
               i = i + 10
           wend

           if initialNumber = number then
              knownPrime = 1
           end if
       end if

       if knownPrime <> 0 then
           print initialNumber; " is prime"
       else
           print initialNumber; " is not prime"
       end if

       print
   end sub

   sub printDivision dividend, divisor
       print dividend; " / "; divisor; " = "; dividend / divisor
   end sub

   ' divide a number by other number while possible
   ' print division to screen
   sub divideWhilePossibleBy byref number, by
       while number mod by = 0
           call printDivision number, by
           number = number / by
       wend
   end sub


When entering 3 or 2 it divided by that number just to say it's prime - this one says it right away! Tried to move as much of the repeating code to subroutines as I could, even if it is a single line - that's a single line I have to change, not 4 different ones in different places  Got rid of gotos too, the only one I had second thoughts about was the [m4] one, kind of made sense at first, but then it was just a case of a condition that will eventually happen, so repeat ad infinitum and watch for the condition.