WHILE AND DO LOOP CYCLES

[Kiara87]

from your advice i searched google and i found this code

but it doesn't work and I don't understand why this code doesn't work?

@Kiara87  No odds/evens, find Prime Numbers from 2 to 100 with the help of an array to store findings. (You don't have to, of course, just trying to find ways to for you to practice with arrays.)

Code: QB64: [Select]

1. DEFLNG A-Z
2. DECLARE SUB BubbleSortInt(a(), Ans)
3. DECLARE SUB FillArrayInt(a())
4. DECLARE SUB ShowArrayInt(a())
5.  
6. SUB BubbleSortInt(a(), Ans)
7.     DIM Var_Swap
8.     DIM Last
9.     DIM i
10.     DIM n
11.     DIM Temp
12.     DIM A1
13.     DIM A2
14.    
15.     n = UBOUND(a) + 1
16.     Var_Swap = 1
17.     Last = n - 1
18.     i = 0
19.     DO WHILE Var_Swap
20.         Var_Swap = 0
21.         FOR i = 0 TO Last - 1
22.             IF a(i) > a(i + 1) THEN
23.                 A1 = a(i)
24.                 A2 = a(i + 1)
25.                 Temp = a(i)
26.                 a(i) = a(i + 1)
27.                 a(i + 1) = Temp
28.                 Var_Swap = 1
29.                 IF Ans = 1 THEN
30.                     PRINT "SWAP     i: " + STR$(A1) + "   i+1: " + STR$(A2)
31.                     ShowArrayInt a
32.                 END IF
33.             END IF
34.         NEXT
35.     LOOP
36. END SUB
37.  
38. SUB FillArrayInt(a())
39.     DIM i
40.     DIM Length
41.    
42.     Length = UBOUND(a) + 1
43.     FOR i = 0 TO Length - 1
44.         a(i) = INT(RND * Length)
45.     NEXT
46. END SUB
47.  
48. SUB ShowArrayInt(a())
49.     DIM i
50.     DIM s$
51.     DIM Length
52.    
53.     Length = UBOUND(a) + 1
54.     s$ = ""
55.     FOR i = 0 TO Length - 1
56.         IF i = Length - 1 THEN
57.             s$ = s$ + STR$(a(i))
58.         ELSE
59.             s$ = s$ + STR$(a(i)) + " "
60.         END IF
61.     NEXT
62.     PRINT s$
63. END SUB
64.  
65. ' Main
66. DIM Num
67. DIM Ans$
68. DIM AnsI
69. DIM i
70.  
71. PRINT "[IT] Quanti elementi? " + CHR$(13) + CHR$(10) + "[EN] Enter no of elements : "
72. INPUT Num
73. PRINT "[IT] Vuoi vedere il contenuto del vettore quando scambio? (S/Y/N)" + CHR$(13) + CHR$(10) + "[EN] Do you want to see swapped elements in array? (S/Y/N)"
74. INPUT Ans$
75. IF Ans$ = "S" OR Ans$ = "s" OR Ans$ = "Y" OR Ans$ = "y" OR LEN(Ans$) > 0 THEN
76.     AnsI = 1
77. ELSE
78.     AnsI = 0
79. END IF
80. DIM Arr(Num)
81.  
82. FillArrayInt Arr
83. PRINT "[IT] Vettore non ordinato: " + CHR$(13) + CHR$(10) + "[EN] Unordered Array: "
84. ShowArrayInt Arr
85. BubbleSortInt Arr, AnsI
86. PRINT "[IT] Vettore ordinato: " + CHR$(13) + CHR$(10) + "[EN] Ordered Array: "
87. ShowArrayInt Arr
88. END
89.  

[TempodiBasic]

@Kiara87
the code that you posted here above isn't original Qb64... to see how it works (runs) you must translate into this one

Code: QB64: [Select]

1. DEFLNG A-Z
2. DECLARE SUB BubbleSortInt(a(), Ans)
3. DECLARE SUB FillArrayInt(a())
4. DECLARE SUB ShowArrayInt(a())
5.  
6. ' Main
7. DIM Num
8. DIM Ans$
9. DIM AnsI
10. DIM i
11.  
12. PRINT "[IT] Quanti elementi? " + CHR$(13) + CHR$(10) + "[EN] Enter no of elements : "
13. INPUT Num
14. PRINT "[IT] Vuoi vedere il contenuto del vettore quando scambio? (S/Y/N)" + CHR$(13) + CHR$(10) + "[EN] Do you want to see swapped elements in array? (S/Y/N)"
15. INPUT Ans$
16. IF Ans$ = "S" OR Ans$ = "s" OR Ans$ = "Y" OR Ans$ = "y" OR LEN(Ans$) > 0 THEN
17.     AnsI = 1
18. ELSE
19.     AnsI = 0
20. END IF
21. DIM Arr(Num)
22.  
23. FillArrayInt Arr()
24. PRINT "[IT] Vettore non ordinato: " + CHR$(13) + CHR$(10) + "[EN] Unordered Array: "
25. ShowArrayInt Arr()
26. BubbleSortInt Arr(), AnsI
27. PRINT "[IT] Vettore ordinato: " + CHR$(13) + CHR$(10) + "[EN] Ordered Array: "
28. ShowArrayInt Arr()
29. END
30.  
31.  
32.  
33. SUB BubbleSortInt (a(), Ans)
34.     DIM Var_Swap
35.     DIM Last
36.     DIM i
37.     DIM n
38.     DIM Temp
39.     DIM A1
40.     DIM A2
41.  
42.     n = UBOUND(a) + 1
43.     Var_Swap = 1
44.     Last = n - 1
45.     i = 0
46.     DO WHILE Var_Swap
47.         Var_Swap = 0
48.         FOR i = 0 TO Last - 1
49.             IF a(i) > a(i + 1) THEN
50.                 A1 = a(i)
51.                 A2 = a(i + 1)
52.                 Temp = a(i)
53.                 a(i) = a(i + 1)
54.                 a(i + 1) = Temp
55.                 Var_Swap = 1
56.                 IF Ans = 1 THEN
57.                     PRINT "SWAP     i: " + STR$(A1) + "   i+1: " + STR$(A2)
58.                     ShowArrayInt a()
59.                 END IF
60.             END IF
61.         NEXT
62.     LOOP
63. END SUB
64.  
65. SUB FillArrayInt (a())
66.     DIM i
67.     DIM Length
68.  
69.     Length = UBOUND(a) + 1
70.     FOR i = 0 TO Length - 1
71.         a(i) = INT(RND * Length)
72.     NEXT
73. END SUB
74.  
75. SUB ShowArrayInt (a())
76.     DIM i
77.     DIM s$
78.     DIM Length
79.  
80.     Length = UBOUND(a) + 1
81.     s$ = ""
82.     FOR i = 0 TO Length - 1
83.         IF i = Length - 1 THEN
84.             s$ = s$ + STR$(a(i))
85.         ELSE
86.             s$ = s$ + STR$(a(i)) + " "
87.         END IF
88.     NEXT
89.     PRINT s$
90. END SUB
91.  
92.  

it is about Bubblesort a fundamental algorhytm about sorting a list of omogeneus things.

@bplus,
yes  the challange is to find Prime Number from 2 to 100, but  a first pass to find Prime Number is to evaluate if the number is even, if yes and more than 2 it is NOT prime number, otherwise if it is ODD I must divide it by its previous numbers to get no integer result to find the Prime Number.

[bplus]

@TempodiBasic

Don't have to do 2's separate:

Code: QB64: [Select]

1. REDIM n(2 TO 100) AS INTEGER
2. n(2) = 2
3. FOR i = 3 TO 100
4.     FOR j = 2 TO SQR(i)
5.         IF i / j = INT(i / j) THEN n(i) = j: EXIT FOR
6.     NEXT
7.     IF n(i) = 0 THEN n(i) = i
8. NEXT
9. PRINT "primes between 2 and 100:"
10. FOR i = 2 TO 100
11.     IF n(i) = i THEN PRINT i,
12. NEXT
13. PRINT: PRINT "Lowest dividers:"
14. FOR i = 2 TO 100
15.     IF n(i) <> i THEN PRINT i; " "; n(i),
16. NEXT
17.  

[TempodiBasic]

@dear Bplus
I think that we can save CPU work using STEP 2 in the external FOR NEXT loop.
In fact the only even Prime number is 2. And with this we reduce to half the work to accomplish by the program.
And as consequence the inner FOR NEXT starts from 3 to SQR(i) step 2 because if we're processing only odd numbers there is no matter to divide by 2 and by its multiplies.
so your code can be converted into this one

Code: QB64: [Select]

1. REDIM n(2 TO 100) AS INTEGER
2. n(2) = 2
3. FOR i = 3 TO 100 STEP 2
4.     FOR j = 3 TO SQR(i) STEP 2
5.         IF i / j = INT(i / j) THEN n(i) = j: EXIT FOR
6.     NEXT
7.     IF n(i) = 0 THEN n(i) = i
8. NEXT
9. PRINT "primes between 2 and 100:"
10. FOR i = 2 TO 100
11.     IF n(i) = i THEN PRINT i,
12. NEXT
13. PRINT: PRINT "Lowest dividers:"
14. FOR i = 2 TO 100
15.     IF n(i) <> i THEN IF n(i) = 0 THEN PRINT i; " 2", ELSE PRINT i; " "; n(i),
16. NEXT
17.  

from 2 to 100 the time difference is minimal, but using _integer64 from 2 to 1.000.000 the difference can be visible.
Thanks to reply to me

[Kiara87]

@dear Bplus
I think that we can save CPU work using STEP 2 in the external FOR NEXT loop.
In fact the only even Prime number is 2. And with this we reduce to half the work to accomplish by the program.
And as consequence the inner FOR NEXT starts from 3 to SQR(i) step 2 because if we're processing only odd numbers there is no matter to divide by 2 and by its multiplies.
so your code can be converted into this one

Code: QB64: [Select]

1. REDIM n(2 TO 100) AS INTEGER
2. n(2) = 2
3. FOR i = 3 TO 100 STEP 2
4.     FOR j = 3 TO SQR(i) STEP 2
5.         IF i / j = INT(i / j) THEN n(i) = j: EXIT FOR
6.     NEXT
7.     IF n(i) = 0 THEN n(i) = i
8. NEXT
9. PRINT "primes between 2 and 100:"
10. FOR i = 2 TO 100
11.     IF n(i) = i THEN PRINT i,
12. NEXT
13. PRINT: PRINT "Lowest dividers:"
14. FOR i = 2 TO 100
15.     IF n(i) <> i THEN IF n(i) = 0 THEN PRINT i; " 2", ELSE PRINT i; " "; n(i),
16. NEXT
17.  

from 2 to 100 the time difference is minimal, but using _integer64 from 2 to 1.000.000 the difference can be visible.
Thanks to reply to me

ciao @TempodiBasic
questo è quello che intendeva bplus?
devo studiare REDIM Non so cosa fa questa istruzione poi vedo un for to nex annidato credo si chiama cosi annidato oppure indentato,
poi un print numeri primi compresi tra 2 e 100
un if che verifica la matrice se è uguale a i dentro al ciclo for è seguenziale un altro for con all interno un if
ci studio un po su questo codice che non mi è chiaro alcune cose che devo capire
grazie per il tuo aiuto

[bplus]

@dear Bplus
I think that we can save CPU work using STEP 2 in the external FOR NEXT loop.
In fact the only even Prime number is 2. And with this we reduce to half the work to accomplish by the program.
And as consequence the inner FOR NEXT starts from 3 to SQR(i) step 2 because if we're processing only odd numbers there is no matter to divide by 2 and by its multiplies.
so your code can be converted into this one

Code: QB64: [Select]

1. REDIM n(2 TO 100) AS INTEGER
2. n(2) = 2
3. FOR i = 3 TO 100 STEP 2
4.     FOR j = 3 TO SQR(i) STEP 2
5.         IF i / j = INT(i / j) THEN n(i) = j: EXIT FOR
6.     NEXT
7.     IF n(i) = 0 THEN n(i) = i
8. NEXT
9. PRINT "primes between 2 and 100:"
10. FOR i = 2 TO 100
11.     IF n(i) = i THEN PRINT i,
12. NEXT
13. PRINT: PRINT "Lowest dividers:"
14. FOR i = 2 TO 100
15.     IF n(i) <> i THEN IF n(i) = 0 THEN PRINT i; " 2", ELSE PRINT i; " "; n(i),
16. NEXT
17.  

from 2 to 100 the time difference is minimal, but using _integer64 from 2 to 1.000.000 the difference can be visible.
Thanks to reply to me

Ah! I see just skip the 2's if n(i) is still 0 then it was divisible by 2, nice one! @TempodiBasic

Yes, there are faster ways to do this when you have a much higher limit to go, I just wanted to get the ball rolling with some code.

[Kernelpanic]

@Kiara87 - Have you solved the task in the meantime? This book is good, maybe it is in Italian too. "MS-DOS QBasic" Handbuch für Programmierer, The Waite Group. Theory and practice. Try the tasks right away. And then think up your own tasks, that's how you learn to program.
http://www.antonis.de/qbuecher/index.htm

Here is another program for finding prime numbers with indication of the number up to input, without an array. From 10,000 the formatting gets out of hand.

Code: QB64: [Select]

1. 'Output of all prime numbers up to input - 14. Nov. 2020
2.  
3. OPTION _EXPLICIT
4.  
5. DIM eingabe AS LONG, anzahlprim AS LONG
6. DIM primzahl AS LONG, j AS LONG
7.  
8. PRINT "Ausgabe aller Primzahlen bis zur Eingabe"
9. INPUT "Alle Primzahlen ausgeben bis: ", eingabe
10.  
11. anzahlprim = 0
12. FOR primzahl = 2 TO eingabe STEP 1
13.   j = 2
14.   DO WHILE primzahl MOD j <> 0
15.     j = j + 1
16.   LOOP
17.   IF j = primzahl THEN PRINT USING "#####"; primzahl;
18.  
19.   IF j = primzahl THEN anzahlprim = anzahlprim + 1
20. NEXT
21. PRINT: PRINT
22. PRINT USING "Bis #### gibt es #### Primzahlen"; eingabe, anzahlprim
23.  
24. END
25.  

[Kernelpanic]

@Kiara87 - For explanation:
For each number -primzahl- it is tried out whether there are other positive factors than 1 and -primzahl-. This is how you find out whether -primzahl- is a prime number or not. Since a divisor of -primzahl- cannot be greater than -primzahl- so you only need to check the -zahlenbereich- between 1 and -primzahl-.
-zahlenbereich- is Number range.

I hope the program is more understandable now.

Code: QB64: [Select]

1. 'Ausgabe aller Primzahlen bis Eingabe - 14. Nov. 2020
2.  
3. OPTION _EXPLICIT
4.  
5. DIM eingabe AS LONG, anzahlprim AS LONG
6. DIM primzahl AS LONG, zahlenbereich AS LONG
7.  
8. PRINT "Ausgabe aller Primzahlen bis zur Eingabe"
9. INPUT "Alle Primzahlen ausgeben bis: ", eingabe
10.  
11. anzahlprim = 0
12. FOR primzahl = 2 TO eingabe STEP 1
13.   zahlenbereich = 2
14.   DO WHILE primzahl MOD zahlenbereich <> 0
15.     zahlenbereich = zahlenbereich + 1
16.   LOOP
17.   IF zahlenbereich = primzahl THEN PRINT USING "#####"; primzahl;
18.  
19.   IF zahlenbereich = primzahl THEN anzahlprim = anzahlprim + 1
20. NEXT
21. PRINT: PRINT
22. PRINT USING "Bis #### gibt es #### Primzahlen"; eingabe, anzahlprim
23.  
24. END
25.  

[Kiara87]

@Kiara87 - For explanation:
For each number -primzahl- it is tried out whether there are other positive factors than 1 and -primzahl-. This is how you find out whether -primzahl- is a prime number or not. Since a divisor of -primzahl- cannot be greater than -primzahl- so you only need to check the -zahlenbereich- between 1 and -primzahl-.
-zahlenbereich- is Number range.

I hope the program is more understandable now.

Code: QB64: [Select]

1. 'Ausgabe aller Primzahlen bis Eingabe - 14. Nov. 2020
2.  
3. OPTION _EXPLICIT
4.  
5. DIM eingabe AS LONG, anzahlprim AS LONG
6. DIM primzahl AS LONG, zahlenbereich AS LONG
7.  
8. PRINT "Ausgabe aller Primzahlen bis zur Eingabe"
9. INPUT "Alle Primzahlen ausgeben bis: ", eingabe
10.  
11. anzahlprim = 0
12. FOR primzahl = 2 TO eingabe STEP 1
13.   zahlenbereich = 2
14.   DO WHILE primzahl MOD zahlenbereich <> 0
15.     zahlenbereich = zahlenbereich + 1
16.   LOOP
17.   IF zahlenbereich = primzahl THEN PRINT USING "#####"; primzahl;
18.  
19.   IF zahlenbereich = primzahl THEN anzahlprim = anzahlprim + 1
20. NEXT
21. PRINT: PRINT
22. PRINT USING "Bis #### gibt es #### Primzahlen"; eingabe, anzahlprim
23.  
24. END
25.  

very understandable thanks

[NOVARSEG]

Ok I like
 
DO
LOOP
****
You can do this only if there is a good reason
DO
    IF whatever GOTO label
LOOP
label:
****

Otherwise

DO
    IF whatever EXIT DO
LOOP