Gambas3 Primes routines

Primes.module

' Gambas module file

Public Sub Main()

  Dim l_bound, u_bound As Integer
  
  Print "Primes between a range [Note: 1 is special and 2 is even Prime]"

  Print "Input lower bound (should be greater than 2)"
  Input l_bound
  
  Print "Input upper bound ( should be greter than lower bound) "; l_bound
  Input u_bound
  Print ""
  Print "Lower bound = "; l_bound; " Upper bound = "; u_bound
  
  primes_between(l_bound, u_bound)
  Dim x As Integer
  Dim a As Array
  
  a = prime_array_between(l_bound, u_bound)
  For x = 0 To a.Length - 1
    Print a[x]
  Next
  ' first 10 primes
  a = prime_array(10)
  For x = 0 To a.Length - 1
    Print a[x]
  Next
End
' checks if a number is prime
' input positive integer
' returns true if the input is prime else false

Public Function is_prime(x As Integer) As Boolean
  
  Dim i As Integer
  For i = 2 To CInt(Ceil(Sqr(x)))
    'Print "--- checking with "; i, x; "%"; i; " = "; x % i
    If x % i = 0 Then
      Return False
    Endif
  Next 
  Return True
End
' make a prime array
' this function creates a dynamic array of integer stores desired numbers of primes
' in it and returns the array
' input number of primes desired 
' output returns array containing desired number of primes 
 
Public Function prime_array(n As Integer) As Integer[]
  
  Dim i, j As Integer
  i = 1
  j = 3
  Dim arr As New Integer[]
  arr.Add(2)
  While i < n
    If is_prime(j) Then 
      arr.Add(j)
      i += 1
    Endif
    j += 1
  Wend
  Return arr
  
End
' prints prime numbers between 2 numbers
' input lower bound , upper bound
' output prints all primes in the inclussive range
Public Sub primes_between(lb As Integer, ub As Integer)
  
  If lb < 3 Then 
    Print 2
    lb = 3
  Endif
  If ub < lb Then
    ub = lb
  Endif
  While lb <= ub
    If is_prime(lb) Then 
      Print lb
    Endif
    lb += 1
  Wend
End

' make a prime array
' this function creates a dynamic array of integer stores primes between range
' in it and returns the array
' input lower bound and upper bound
' output returns array containing primes inclusive of bounds 
Public Function prime_array_between(lb As Integer, ub As Integer) As Integer[]
  
  Dim arr As New Integer[]
  If lb < 3 Then 
    arr.Add(2)
    lb = 3
  Endif
  If ub < lb Then
    ub = lb
  Endif
  While lb <= ub
    If is_prime(lb) Then 
      arr.Add(lb)
    Endif
    lb += 1
  Wend
  Return arr
End