Mathematica Tutorial

Expressions as Trees

Here is an expression in full form.

Out[1]//FullForm=

TreeForm prints out expressions to show their "tree" structure.

In[2]:=

Out[2]//TreeForm=

You can think of any Mathematica expression as a tree. In the expression above, the top node in the tree consists of a Plus. From this node come two "branches", x^3 and (1+x)^2. From the x^3 node, there are then two branches, x and 3, which can be viewed as "leaves" of the tree.

This matrix is a simple tree with just two levels.

In[3]:=

Out[3]//TreeForm=

Here is a more complicated expression.

In[4]:=

Out[4]=

The tree for this expression has several levels. The representation of the tree here was too long to fit on a single line, so it had to be broken onto two lines.

In[5]:=

Out[5]//TreeForm=

The indices that label each part of an expression have a simple interpretation in terms of trees. Descending from the top node of the tree, each index specifies which branch to take in order to reach the part you want.