| package jp.ac.kobe_u.cs.prolog.lang; |
| import java.io.Serializable; |
| /** |
| * Choice point frame.<br> |
| * |
| * @author Mutsunori Banbara (banbara@kobe-u.ac.jp) |
| * @author Naoyuki Tamura (tamura@kobe-u.ac.jp) |
| * @version 1.0 |
| */ |
| class CPFEntry implements Serializable { |
| public long timeStamp; |
| public Term[] args; // argument register |
| public Predicate cont; // continuation goal |
| public Predicate bp; // next cluase |
| public int tr; // trail pointer |
| public int b0; // cut point |
| |
| protected CPFEntry(Term[] args, Predicate cont){ |
| this.args = args; |
| this.cont = cont; |
| } |
| |
| public String toString() { |
| String t = " time:" + timeStamp + "\n" ; |
| t = t + "args:"; |
| for (int i=0; i<args.length; i++) { |
| t = t + args[i] + " "; |
| } |
| t = t + "\n"; |
| t = t + " cont:" + cont + "\n"; |
| t = t + " bp:" + bp + "\n"; |
| t = t + " tr:" + tr + "\n"; |
| t = t + " b0:" + b0 + "\n"; |
| return t; |
| } |
| } |
| |
| /** |
| * Choice point frame stack.<br> |
| * The <code>CPFStack</code> class represents a stack |
| * of choice point frames.<br> |
| * Each choice point frame has the following fields: |
| * <ul> |
| * <li><em>arguments</em> |
| * <li><em>continuation goal</em> |
| * <li><em>next clause</em> |
| * <li><em>trail pointer</em> |
| * <li><em>cut point</em> |
| * <li><em>time stamp</em> |
| * </ul> |
| * |
| * @author Mutsunori Banbara (banbara@kobe-u.ac.jp) |
| * @author Naoyuki Tamura (tamura@kobe-u.ac.jp) |
| * @version 1.0 |
| */ |
| public class CPFStack implements Serializable { |
| /** Maximum size of enties. Initial size is <code>20000</code>. */ |
| protected int maxContents = 20000; |
| |
| /** An array of choice point frames. */ |
| protected CPFEntry[] buffer; |
| |
| /** the top index of this <code>CPFStack</code>. */ |
| protected int top; |
| |
| /** Holds the Prolog engine that this <code>CPFStack</code> belongs to. */ |
| protected Prolog engine; |
| |
| /** Constructs a new choice point frame stack. */ |
| public CPFStack(Prolog _engine) { |
| engine = _engine; |
| buffer = new CPFEntry[maxContents]; |
| top = -1; |
| } |
| |
| /** Constructs a new choice point frame stack with the given size. */ |
| public CPFStack(Prolog _engine, int n) { |
| engine = _engine; |
| maxContents = n; |
| buffer = new CPFEntry[maxContents]; |
| top = -1; |
| } |
| |
| /** Create a new choice point frame. |
| * @param args <em>arguments</em> |
| * @param p a <em>continuation goal</em> |
| */ |
| public void create(Term[] args, Predicate p){ |
| try { |
| buffer[++top] = new CPFEntry(args, p); |
| } catch (ArrayIndexOutOfBoundsException e) { |
| System.out.println("{expanding choice point stack...}"); |
| int len = buffer.length; |
| CPFEntry[] new_buffer = new CPFEntry[len+10000]; |
| for(int i=0; i<len; i++) { |
| new_buffer[i] = buffer[i]; |
| } |
| buffer = new_buffer; |
| buffer[top] = new CPFEntry(args, p); |
| maxContents = len+10000; |
| } |
| } |
| |
| /** Discards all choice points. */ |
| public void deleteAll() { |
| while (! empty()) { |
| buffer[top--] = null; |
| } |
| } |
| |
| /** Discards all choice points after the value of <code>i</code>. */ |
| public void cut(int i) { |
| while (top > i) { |
| buffer[top--] = null; |
| } |
| } |
| |
| /** Discards the top of choice points. */ |
| public void delete() { buffer[top--] = null; } |
| |
| /** Discards all choice points. */ |
| public void init() { deleteAll(); } |
| |
| /** Tests if this stack has no entry. */ |
| public boolean empty() { return top == -1; } |
| |
| /** Returns the value of <code>top</code>. |
| * @see #top |
| */ |
| public int top() { return top; } |
| |
| /** Returns the value of <code>maxContents</code>. |
| * @see #maxContents |
| */ |
| public int max() { return maxContents; } |
| |
| /** Returns the <em>arguments</em> of current choice point frame. */ |
| public Term[] getArgs() { return buffer[top].args; } |
| |
| /** Returns the <em>continuation goal</em> of current choice point frame. */ |
| public Predicate getCont() { return buffer[top].cont; } |
| |
| /** Returns the <em>time stamp</em> of current choice point frame. */ |
| public long getTimeStamp() { return buffer[top].timeStamp; } |
| /** Sets the <em>time stamp</em> of current choice point frame. */ |
| public void setTimeStamp(long t) { buffer[top].timeStamp = t; } |
| |
| /** Returns the <em>next clause</em> of current choice point frame. */ |
| public Predicate getBP() { return buffer[top].bp; } |
| /** Sets the <em>next clause</em> of current choice point frame. */ |
| public void setBP(Predicate p) { buffer[top].bp = p; } |
| |
| /** Returns the <em>trail pointer</em> of current choice point frame. */ |
| public int getTR() { return buffer[top].tr; } |
| /** Sets the <em>trail pointer</em> of current choice point frame. */ |
| public void setTR(int i) { buffer[top].tr = i; } |
| |
| /** Returns the <em>cut point</em> of current choice point frame. */ |
| public int getB0() { return buffer[top].b0; } |
| /** Sets the <em>cut point</em> of current choice point frame. */ |
| public void setB0(int i) { buffer[top].b0 = i; } |
| |
| /** Shows the contents of this <code>CPFStack</code>. */ |
| public void show() { |
| if (empty()) { |
| System.out.println("{choice point stack is empty!}"); |
| return; |
| } |
| for (int i=0; i<=top; i++) { |
| System.out.print("stack[" + i + "]: "); |
| System.out.println(buffer[i]); |
| } |
| } |
| } |