1 files changed, 104 insertions, 0 deletions
diff --git a/extraplugins/facade/org.eclipse.papyrus.facade.definition.editor/src/org/eclipse/papyrus/facadeSpecificEditor/utils/CombinationGenerator.java b/extraplugins/facade/org.eclipse.papyrus.facade.definition.editor/src/org/eclipse/papyrus/facadeSpecificEditor/utils/CombinationGenerator.java
new file mode 100644
index 00000000000..88b2a2917d3
--- /dev/null
+++ b/extraplugins/facade/org.eclipse.papyrus.facade.definition.editor/src/org/eclipse/papyrus/facadeSpecificEditor/utils/CombinationGenerator.java
@@ -0,0 +1,104 @@
+package org.eclipse.papyrus.facadeSpecificEditor.utils;
+
+import java.math.BigInteger;
+
+public class CombinationGenerator {
+	private int[] a;
+	private int n;
+	private int r;
+	private BigInteger numLeft;
+	private BigInteger total;
+
+	// ------------
+	// Constructor
+	// ------------
+
+	public CombinationGenerator(int n, int r) {
+		if (r > n) {
+			throw new IllegalArgumentException();
+		}
+		if (n < 1) {
+			throw new IllegalArgumentException();
+		}
+		this.n = n;
+		this.r = r;
+		a = new int[r];
+		BigInteger nFact = getFactorial(n);
+		BigInteger rFact = getFactorial(r);
+		BigInteger nminusrFact = getFactorial(n - r);
+		total = nFact.divide(rFact.multiply(nminusrFact));
+		reset();
+	}
+
+	// ------
+	// Reset
+	// ------
+
+	public void reset() {
+		for (int i = 0; i < a.length; i++) {
+			a[i] = i;
+		}
+		numLeft = new BigInteger(total.toString());
+	}
+
+	// ------------------------------------------------
+	// Return number of combinations not yet generated
+	// ------------------------------------------------
+
+	public BigInteger getNumLeft() {
+		return numLeft;
+	}
+
+	// -----------------------------
+	// Are there more combinations?
+	// -----------------------------
+
+	public boolean hasMore() {
+		return numLeft.compareTo(BigInteger.ZERO) == 1;
+	}
+
+	// ------------------------------------
+	// Return total number of combinations
+	// ------------------------------------
+
+	public BigInteger getTotal() {
+		return total;
+	}
+
+	// ------------------
+	// Compute factorial
+	// ------------------
+
+	private static BigInteger getFactorial(int n) {
+		BigInteger fact = BigInteger.ONE;
+		for (int i = n; i > 1; i--) {
+			fact = fact.multiply(new BigInteger(Integer.toString(i)));
+		}
+		return fact;
+	}
+
+	// --------------------------------------------------------
+	// Generate next combination (algorithm from Rosen p. 286)
+	// --------------------------------------------------------
+
+	public int[] getNext() {
+
+		if (numLeft.equals(total)) {
+			numLeft = numLeft.subtract(BigInteger.ONE);
+			return a;
+		}
+
+		int i = r - 1;
+		while (a[i] == n - r + i) {
+			i--;
+		}
+		a[i] = a[i] + 1;
+		for (int j = i + 1; j < r; j++) {
+			a[j] = a[i] + j - i;
+		}
+
+		numLeft = numLeft.subtract(BigInteger.ONE);
+		return a;
+
+	}
+}