1 files changed, 129 insertions, 0 deletions
diff --git a/T0/SType.cs b/T0/SType.cs
new file mode 100644
index 000000000000..80e9f0176e18
--- /dev/null
+++ b/T0/SType.cs
@@ -0,0 +1,129 @@
+using System;
+
+/*
+ * This structure contains the stack effect of a word: number of stack
+ * element consumed on input, and number of stack element produced on
+ * output.
+ */
+
+struct SType {
+
+	/*
+	 * Get number of stack elements consumed on input; this is -1 if
+	 * the stack effect is not known.
+	 */
+	internal int DataIn {
+		get {
+			return din;
+		}
+	}
+
+	/*
+	 * Get number of stack elements produced on output; this is -1 if
+	 * either the stack effect is not known, or if the word never
+	 * exits.
+	 */
+	internal int DataOut {
+		get {
+			return dout;
+		}
+	}
+
+	/*
+	 * Tell whether the stack effect is known.
+	 */
+	internal bool IsKnown {
+		get {
+			return din >= 0;
+		}
+	}
+
+	/*
+	 * Tell whether the stack effect is known and the word never exits.
+	 */
+	internal bool NoExit {
+		get {
+			return din >= 0 && dout < 0;
+		}
+	}
+
+	int din, dout;
+
+	internal SType(int din, int dout)
+	{
+		if (din < 0) {
+			din = -1;
+		}
+		if (dout < 0) {
+			dout = -1;
+		}
+		this.din = din;
+		this.dout = dout;
+	}
+
+	/*
+	 * Special value for the unknown stack effect.
+	 */
+	internal static SType UNKNOWN = new SType(-1, -1);
+
+	/*
+	 * Constant for the "blank stack effect".
+	 */
+	internal static SType BLANK = new SType(0, 0);
+
+	public static bool operator ==(SType s1, SType s2)
+	{
+		return s1.din == s2.din && s1.dout == s2.dout;
+	}
+
+	public static bool operator !=(SType s1, SType s2)
+	{
+		return s1.din != s2.din || s1.dout != s2.dout;
+	}
+
+	public override bool Equals(Object obj)
+	{
+		return (obj is SType) && ((SType)obj == this);
+	}
+
+	public override int GetHashCode()
+	{
+		return din * 31 + dout * 17;
+	}
+
+	public override string ToString()
+	{
+		if (!IsKnown) {
+			return "UNKNOWN";
+		} else if (NoExit) {
+			return string.Format("in:{0},noexit", din);
+		} else {
+			return string.Format("in:{0},out:{1}", din, dout);
+		}
+	}
+
+	/*
+	 * Test whether this stack effect is a sub-effect of the provided
+	 * stack effect s. Stack effect s1 is a sub-effect of stack-effect
+	 * s2 if any of the following holds:
+	 * -- s1 and s2 are known, s1.din <= s2.din and s1 does not exit.
+	 * -- s1 and s2 are known, s1.din <= s2.din, s1 and s2 exit,
+	 *    and s1.din - s1.dout == s2.din - s2.dout.
+	 */
+	internal bool IsSubOf(SType s)
+	{
+		if (!IsKnown || !s.IsKnown) {
+			return false;
+		}
+		if (din > s.din) {
+			return false;
+		}
+		if (NoExit) {
+			return true;
+		}
+		if (s.NoExit) {
+			return false;
+		}
+		return (din - dout) == (s.din - s.dout);
+	}
+}