The left shift operator (« operator$shl) is overloaded for several object mostly to symbolize the forwarding of an information into an object.

The left shift operator can be used to add values to a Dataset or a DatasetRef. Every left shift describes a new column in a row of the dataset.

dataset("test") << 1 << 2;
dataset("test") << 11 << 12;

this results in:

module A(float len, float fact);
protected void init ()
[
	Axiom ==> A(2,5) A(5,1) A(1,1);
]
 
public void run ()
{
 dataset("test") << (*a:A*).getId() << a[len] << a[fact] << a[len]*a[fact];
 
}

Similar to the datasets the left shift operator is defined for GroIMP's list objects.

• de.grogra.xl.util.ByteList
• de.grogra.xl.util.ShortList
• de.grogra.xl.util.CharList
• de.grogra.xl.util.IntList
• de.grogra.xl.util.LongList
• de.grogra.xl.util.FloatList
• de.grogra.xl.util.DoubleList
• java.util.List
  • e.g ArrayList

The difference to the datasets its that this lists are only one dimensional, therefore all elements are added in a chain/list.

import de.grogra.xl.util.FloatList;
 
...
 
FloatList x = new FloatList();
 
x << 1 << 2 << 3;
x << 4 << 5;
 
println(x);//de.grogra.xl.util.FloatList@8194d89f{1.0, 2.0, 3.0, 4.0, 5.0}

The left shift can also be used to “send” information to a java PrintWriter object (java.io.PrintWriter). This can be used to create output files:

 
module A(float len, float fact);
protected void init ()
[
	Axiom ==> A(2,5) A(5,1) A(1,1);
]
public void run ()
{
 
java.io.PrintWriter output = new java.io.PrintWriter("/home/tim/pwTest.txt");
 
 output << (*a:A*).getId() << "," << a[len] << "," << a[fact] << "," << a[len]*a[fact] << "\n";
output.close();
}

Or it can be used with the out object, a static PrintWriter that represents the XL console. In this case out << "test" is the same as print("test");

The left shift can be used to forward the transformation matrix (Matrix4d) of a node that extends Null(de.grogra.imp3d.objects.Null) to another Null extending node.

This can be used to rewrite a node while keeping the applied local transformation.

protected void init ()
[
	Axiom ==> Box;
]
public void run ()
[
	b:Box ==> Sphere.(b >> $);
]

In the example above the box can be moved/rotated/scaled with the UI tools and after the run function is executed the Box is in the same position. The same effect can be described explicitly with b:Box ==> Sphere.($[transform]=b[transform]);.

This also works with Matrix4d objects as input or output.

The shl operator can be used to add a GRSVertex as a neighbor to a VVQueue.