Initial data commit

Task/Forward-difference/BBC-BASIC/forward-difference.basic

@@ -0,0 +1,30 @@
+      DIM A(9)
+      A() = 90.0, 47.0, 58.0, 29.0, 22.0, 32.0, 55.0, 5.0, 55.0, 73.0
+      PRINT "Original array: " FNshowarray(A())
+      PROCforward_difference(1, A(), B())
+      PRINT "Forward diff 1: " FNshowarray(B())
+      PROCforward_difference(2, A(), C())
+      PRINT "Forward diff 2: " FNshowarray(C())
+      PROCforward_difference(9, A(), D())
+      PRINT "Forward diff 9: " FNshowarray(D())
+      END
+
+      DEF PROCforward_difference(n%, a(), RETURN b())
+      LOCAL c%, i%, j%
+      DIM b(DIM(a(),1) - n%)
+      FOR i% = 0 TO DIM(b(),1)
+        b(i%) = a(i% + n%)
+        c% = 1
+        FOR j% = 1 TO n%
+          c% = -INT(c% * (n% - j% + 1) / j% + 0.5)
+          b(i%) += c% * a(i% + n% - j%)
+        NEXT
+      NEXT
+      ENDPROC
+
+      DEF FNshowarray(a())
+      LOCAL i%, a$
+      FOR i% = 0 TO DIM(a(),1)
+        a$ += STR$(a(i%)) + ", "
+      NEXT
+      = LEFT$(LEFT$(a$))