Add utility functions for QIRList

src/qir/ast/data/QIRList.java

 package qir.ast.data;
 
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.function.BiConsumer;
+import java.util.function.Function;
+import java.util.function.Predicate;
+
 import com.oracle.truffle.api.source.SourceSection;
 
 import qir.ast.QIRNode;
@@ -13,6 +19,43 @@ public abstract class QIRList extends QIRNode {
         super(source);
     }
 
+    private final QIRList iterate(final Predicate<QIRNode> p, final BiConsumer<Deque<QIRNode>, QIRNode> c) {
+        if (this instanceof QIRLnil)
+            return this;
+
+        final Deque<QIRNode> tmp = new ArrayDeque<>();
+        QIRList result = QIRLnil.getInstance();
+
+        for (QIRNode e = this; e instanceof QIRLcons && p.test(e); e = ((QIRLcons) e).getTail())
+            c.accept(tmp, ((QIRLcons) e).getValue());
+        for (QIRNode e : tmp)
+            result = new QIRLcons(null, e, result);
+        return result;
+    }
+
+    private final QIRList iterateAll(final BiConsumer<Deque<QIRNode>, QIRNode> c) {
+        return iterate(e -> true, c);
+    }
+
+    public final QIRList map(final Function<QIRNode, QIRNode> f) {
+        return iterateAll((stack, e) -> stack.push(f.apply(e)));
+    }
+
+    public final QIRList filter(final Function<QIRNode, Boolean> f) {
+        return iterateAll((stack, e) -> {
+            if (f.apply(e))
+                stack.push(e);
+        });
+    }
+
+    // TODO: That is ugly.
+    private long tmpLimit;
+
+    public final QIRList limit(final long limit) {
+        tmpLimit = limit;
+        return iterate(e -> tmpLimit-- > 0, (stack, e) -> stack.add(e));
+    }
+
     @Override
     public <T> T accept(final IQIRVisitor<T> visitor) {
         return visitor.visit(this);

src/qir/ast/operator/QIRFilter.java

 package qir.ast.operator;
 
-import java.util.ArrayDeque;
-import java.util.Deque;
-
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.nodes.UnexpectedResultException;
 import com.oracle.truffle.api.source.SourceSection;
 
 import qir.ast.QIRApply;
 import qir.ast.QIRNode;
-import qir.ast.data.QIRLcons;
 import qir.ast.data.QIRList;
-import qir.ast.data.QIRLnil;
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 import qir.util.QIRException;
@@ -67,21 +62,13 @@ public final class QIRFilter extends QIROperator {
         } catch (UnexpectedResultException e) {
             throw new QIRException("Expected list as input in QIRFilter");
         }
-        final Deque<QIRNode> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
-
-        if (input instanceof QIRLnil)
-            return input;
-        for (QIRNode e = input; e instanceof QIRLcons; e = ((QIRLcons) e).getTail())
+        return input.filter(e -> {
             try {
-                if (new QIRApply(null, f, ((QIRLcons) e).getValue()).executeBoolean(frame).isTrue())
-                    tmp.push(((QIRLcons) e).getValue());
-            } catch (UnexpectedResultException e1) {
+                return new QIRApply(null, f, e).executeBoolean(frame).isTrue();
+            } catch (UnexpectedResultException e2) {
                 throw new QIRException("Expected boolean as result of configuration application in QIRFilter");
             }
-        while (!tmp.isEmpty())
-            result = new QIRLcons(null, tmp.pop(), result);
-        return result;
+        });
     }
 
     @Override

src/qir/ast/operator/QIRLimit.java

 package qir.ast.operator;
 
-import java.util.ArrayDeque;
-import java.util.Deque;
-
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.nodes.UnexpectedResultException;
 import com.oracle.truffle.api.source.SourceSection;
 
 import qir.ast.QIRNode;
-import qir.ast.data.QIRLcons;
-import qir.ast.data.QIRLnil;
+import qir.ast.data.QIRList;
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 import qir.util.QIRException;
@@ -63,18 +59,9 @@ public final class QIRLimit extends QIROperator {
         } catch (UnexpectedResultException e) {
             throw new QIRException("Expected number as configuration in QIRLimit");
         }
-        final long tmp = longLimit;
         try {
-            QIRNode src = child.executeList(frame);
-            final Deque<QIRNode> nodes = new ArrayDeque<>();
-            while (src instanceof QIRLcons && tmp > 0) {
-                nodes.add(((QIRLcons) src).getValue());
-                src = ((QIRLcons) src).getTail();
-            }
-            QIRNode res = QIRLnil.getInstance();
-            for (QIRNode node : nodes)
-                res = new QIRLcons(null, node, res);
-            return res;
+            QIRList src = child.executeList(frame);
+            return src.limit(longLimit);
         } catch (UnexpectedResultException e) {
             throw new QIRException("Expected list as input in QIRLimit");
         }

src/qir/ast/operator/QIRProject.java

 package qir.ast.operator;
 
-import java.util.ArrayDeque;
-import java.util.Deque;
-
 import com.oracle.truffle.api.frame.VirtualFrame;
 import com.oracle.truffle.api.nodes.UnexpectedResultException;
 import com.oracle.truffle.api.source.SourceSection;
 
 import qir.ast.QIRApply;
 import qir.ast.QIRNode;
-import qir.ast.data.QIRLcons;
 import qir.ast.data.QIRList;
-import qir.ast.data.QIRLnil;
 import qir.driver.IQIRVisitor;
 import qir.util.QIRAny;
 import qir.util.QIRException;
@@ -67,16 +62,7 @@ public final class QIRProject extends QIROperator {
         } catch (UnexpectedResultException e) {
             throw new QIRException("Expected list as input for QIRProject");
         }
-        final Deque<QIRNode> tmp = new ArrayDeque<>();
-        QIRList result = QIRLnil.getInstance();
-
-        if (input instanceof QIRLnil)
-            return input;
-        for (QIRNode e = input; e instanceof QIRLcons; e = ((QIRLcons) e).getTail())
-            tmp.push(new QIRApply(null, f, ((QIRLcons) e).getValue()).executeGeneric(frame));
-        while (!tmp.isEmpty())
-            result = new QIRLcons(null, tmp.pop(), result);
-        return result;
+        return input.map(e -> new QIRApply(null, f, e).executeGeneric(frame));
     }
 
     @Override