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+' Challenge 003
+'
+' Challenge #1
+' Create a script to generate 5-smooth numbers, whose prime divisors are less
+' or equal to 5. They are also called Hamming/Regular/Ugly numbers. For more
+' information, please check this wikipedia.
+
+' deque of integers
+type ElemType
+    nValue as integer
+    pNext as ElemType ptr
+end type
+
+type QType
+    pFront as ElemType ptr
+    pBack as ElemType ptr
+end type
+
+function QEmpty(byref q as QType) as boolean
+    if q.pFront = 0 then
+        QEmpty = true
+    else
+        QEmpty = false
+    end if
+end function
+
+function QFront(byref q as QType) as integer
+    QFront = q.pFront->nValue
+end function
+
+function QBack(byref q as QType) as integer
+    QBack = q.pBack->nValue
+end function
+
+sub QPushBack(byref q as QType, nValue as integer)
+    dim pElem as ElemType ptr
+
+    pElem = callocate(1, sizeof(ElemType))
+    pElem->nValue = nValue
+
+    if q.pFront = 0 then
+        q.pFront = pElem
+        q.pBack = pElem
+    else
+        q.pBack->pNext = pElem
+        q.pBack = pElem
+    end if
+end sub
+
+sub QPopBack(byref q as QType)
+    dim pElem as ElemType ptr
+
+    if q.pFront = 0 then            ' empty
+    elseif q.pFront = q.pBack then  ' only one element
+        deallocate q.pFront
+        q.pFront = 0
+        q.pBack = 0
+    else                            ' more than one element
+        pElem = q.pFront
+        do while pElem->pNext <> q.pBack
+            pElem = pElem->pNext
+        loop
+        deallocate q.pBack
+        q.pBack = pElem
+        pElem->pNext = 0
+    end if
+end sub
+
+sub QPushFront(byref q as QType, nValue as integer)
+    dim pElem as ElemType ptr
+
+    pElem = callocate(1, sizeof(ElemType))
+    pElem->nValue = nValue
+
+    if q.pFront = 0 then
+        q.pFront = pElem
+        q.pBack = pElem
+    else
+        pElem->pNext = q.pFront
+        q.pFront = pElem
+    end if
+end sub
+
+sub QPopFront(byref q as QType)
+    dim pElem as ElemType ptr
+
+    if q.pFront = 0 then            ' empty
+    elseif q.pFront = q.pBack then  ' only one element
+        deallocate q.pFront
+        q.pFront = 0
+        q.pBack = 0
+    else                            ' more than one element
+        pElem = q.pFront
+        q.pFront = pElem->pNext
+        deallocate pElem
+    end if
+end sub
+
+
+function min(a as integer, b as integer) as integer
+    if a < b then
+        min = a
+    else
+        min = b
+    end if
+end function
+
+function min3(a as integer, b as integer, c as integer) as integer
+    min3 = min(a, min(b, c))
+end function
+
+
+' Hamming generator
+dim shared q2 as QType
+dim shared q3 as QType
+dim shared q5 as QType
+
+function next_hamming() as integer
+    dim n as integer
+
+    ' init queues at start
+    if QEmpty(q2) then
+        QPushBack q2, 1
+        QPushBack q3, 1
+        QPushBack q5, 1
+    end if
+
+    ' get the smallest of the queue heads
+    n = min3(QFront(q2), QFront(q3), QFront(q5))
+
+    ' shift used multiples
+    if n = QFront(q2) then QPopFront q2
+    if n = QFront(q3) then QPopFront q3
+    if n = QFront(q5) then QPopFront q5
+
+    ' push next multiples
+    QPushBack q2, 2*n
+    QPushBack q3, 3*n
+    QPushBack q5, 5*n
+
+    next_hamming = n
+end function
+
+' main
+dim i as integer
+for i=1 to val(command(1))
+    print trim(str(next_hamming()))
+next i