Initial data commit

Task/Greatest-common-divisor/XBasic/greatest-common-divisor.basic

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+' Greatest common divisor
+PROGRAM "gcddemo"
+VERSION "0.001"
+
+DECLARE FUNCTION Entry()
+DECLARE FUNCTION GcdRecursive(u&, v&)
+DECLARE FUNCTION GcdIterative(u&, v&)
+DECLARE FUNCTION GcdBinary(u&, v&)
+
+FUNCTION Entry()
+  m& = 49865
+  n& = 69811
+  PRINT "GCD("; LTRIM$(STR$(m&)); ","; n&; "):"; GcdIterative(m&, n&); " (iterative)"
+  PRINT "GCD("; LTRIM$(STR$(m&)); ","; n&; "):"; GcdRecursive(m&, n&); " (recursive)"
+  PRINT "GCD("; LTRIM$(STR$(m&)); ","; n&; "):"; GcdBinary (m&, n&); " (binary)"
+END FUNCTION
+
+FUNCTION GcdRecursive(u&, v&)
+  IF u& MOD v& <> 0 THEN
+    RETURN GcdRecursive(v&, u& MOD v&)
+  ELSE
+    RETURN v&
+  END IF
+END FUNCTION
+
+FUNCTION GcdIterative(u&, v&)
+  DO WHILE v& <> 0
+    t& = u&
+    u& = v&
+    v& = t& MOD v&
+  LOOP
+  RETURN ABS(u&)
+END FUNCTION
+
+FUNCTION GcdBinary(u&, v&)
+  u& = ABS(u&)
+  v& = ABS(v&)
+  IF u& < v& THEN
+    t& = u&
+    u& = v&
+    v& = t&
+  END IF
+  IF v& = 0 THEN
+    RETURN u&
+  ELSE
+    k& = 1
+    DO WHILE (u& MOD 2 = 0) && (v& MOD 2 = 0)
+      u& = u& >> 1
+      v& = v& >> 1
+      k& = k& << 1
+    LOOP
+    IF u& MOD 2 = 0 THEN
+      t& = u&
+    ELSE
+      t& = -v&
+    END IF
+    DO WHILE t& <> 0
+      DO WHILE t& MOD 2 = 0
+        t& = t& \ 2
+      LOOP
+      IF t& > 0 THEN
+        u& = t&
+      ELSE
+        v& = -t&
+      END IF
+      t& = u& - v&
+    LOOP
+    RETURN u& * k&
+  END IF
+END FUNCTION
+
+END PROGRAM