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Java/clang/thales/Task.java

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+/*   
+Task.java
+ *    
+ *    You may use and distribute under the terms of either the GNU Lesser
+ *    General Public License, either version 2 of the license or,
+ *    at your choice, any later version. Alternatively, you may use and
+ *    distribute under the terms of the XPL.
+ *
+ *    See the LICENSE.lgpl and LICENSE.xpl files for the specific terms of 
+ *    the licenses.
+ *
+ *    This software is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the README
+ *    file for more details.
+ *
+ */
+/*
+ * Written by Antti-Juhani Kaijanaho.
+ */
+
+package org.gzigzag.clang.thales.*;
+
+import org.gzigzag.*;
+
+class Task {
+    private ZZCell cell;
+
+    public Environment getCurrentEnvironment() {
+        return new Environment(ZZCursorReal.get(cell));
+    }
+
+    public void setCurrentEnvironment(Environment e) {
+        ZZCursorReal.set(cell, e.getCell());
+    }
+
+    public void push(ZZCell c) {
+        ZZCell ct = peek();
+        if (ct != null) {
+            c.connect(DimensionNames.stack, 1, ct);
+            cell.disconnect(DimensionNames.stackptr, 1);
+        }
+        cell.connect(DimensionNames.stackptr, 1, c);
+    }
+
+    public void pop() {
+        ZZCell ct = peek();
+        if (ct == null) throw ZZError("empty Thales Clang runtime stack");
+        ZZCell nt = ct.s(DimensionNames.stack, 1);
+        cell.disconnect(DimensionNames.stackptr, 1);
+        if (nt != null) cell.connect(DimensionNames.stackptr, 1, nt);
+        nt.disconnect(DimensionNames.stack, -1);
+    }
+
+    public ZZCell peek() {
+        return cell.s(DimensionNames.stackptr, 1);
+    }
+
+    public void remove(ZZCell c) {
+        {
+            ZZCell nei = c.s(DimensionNames.stackptr, -1);
+            if (nei.equals(cell)) {
+                pop();
+                return;
+            }
+        }
+
+        for (ZZCell i = peek(); i != null && !i.equals(c);
+             i = i.s(DimensionNames.stack, 1)) {
+            // nothing
+        }
+        if (i == null) throw ZZError("cannot remove that which is not there");
+
+        c.deleteFromRank(DimensionNames.stack);
+    }
+
+    public boolean empty(ZZCell c) {
+        return peek() == null;
+    }
+
+}