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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);
}
}
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