Data update

Task/Earliest-difference-between-prime-gaps/FreeBASIC/earliest-difference-between-prime-gaps.basic

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+Type PrimeGaps
+    As Ulong lastPrime
+    As Ulongint gapStarts(1 To 1e7)
+End Type
+
+Function NextPrime(n As Ulong) As Ulong
+    Dim As Ulong j, i = n + 1
+    Do
+        For j = 2 To Sqr(i)
+            If i Mod j = 0 Then Exit For
+        Next j
+        If j > Sqr(i) Then Return i
+        i += 1
+    Loop
+End Function
+
+Function findGapStart(Byref pg As PrimeGaps, gap As Ulongint) As Ulongint
+    Dim As Ulongint prev, diff
+    If pg.gapStarts(gap) <> 0 Then Return pg.gapStarts(gap)
+    Do
+        prev = pg.lastPrime
+        pg.lastPrime = NextPrime(pg.lastPrime)
+        diff = pg.lastPrime - prev
+        pg.gapStarts(diff) = prev
+        If gap = diff Then Return prev
+    Loop
+End Function
+
+Dim Shared As PrimeGaps pg
+pg.lastPrime = NextPrime(2)
+Dim As Ulongint limit = 1e7
+Dim As Integer pm = 10
+Dim As Ulongint start1, start2, gap1 = 2, gap2, diff
+Do
+    start1 = findGapStart(pg, gap1)
+    gap2 = gap1 + 2
+    start2 = findGapStart(pg, gap2)
+    diff = Abs(start2 - start1)
+    If diff > pm Then
+        Print "Earliest difference >"; pm; " between adjacent prime gap starting primes:"
+        Print "Gap "; gap1; " starts at "; start1; ", gap "; gap2; " starts at "; start2; ", difference is "; diff; !".\n"
+        If pm = limit Then Exit Do
+        pm *= 10
+    Else
+        gap1 = gap2
+    End If
+Loop
+
+Sleep