Data commit

Task/Pells-equation/FreeBASIC/pells-equation.basic

@@ -0,0 +1,24 @@
+Sub Fun(Byref a As LongInt, Byref b As LongInt, c As Integer)
+    Dim As LongInt t
+    t = a : a = b : b = b * c + t
+End Sub
+
+Sub SolvePell(n As Integer, Byref a As LongInt, Byref b As LongInt)
+    Dim As Integer z, r
+    Dim As LongInt x, y, e1, e2, f1, f2
+    x = Sqr(n) : y = x : z  = 1 : r  = 2 * x
+    e1 = 1 : e2 = 0 : f1 = 0 : f2 = 1
+    While True
+        y = r * z - y : z = (n - y * y) / z : r = (x + y) / z
+        Fun(e1, e2, r) : Fun(f1, f2, r) : a = f2 : b = e2 : Fun(b, a, x)
+        If a * a - n * b * b = 1 Then Exit Sub
+    Wend
+End Sub
+
+Dim As Integer i
+Dim As LongInt x, y
+Dim As Integer n(0 To 3) = {61, 109, 181, 277}
+For i = 0 To 3 ''n In {61, 109, 181, 277}
+    SolvePell(n(i), x, y)
+    Print Using "x^2 - ### * y^2 = 1 for x = ##################### and y = #####################"; n(i); x; y
+Next i