Construct a tree from the structure of an expression:

Include heads:

Specify the structure to use:

Construct a tree from symbolic XML:

Construct a tree from an unevaluated expression:

Construct a tree from nested associations:

Construct a tree from the structure of a complicated antiderivative:

Construct a tree from an expression:

Get back the original expression:

Transform a tree into an expression:

Transform the resulting expression back into a tree:

Construct trees from groupings of a list:

With the default structure "HeadTrees", ExpressionTree constructs a tree with subtrees containing data giving the tree structure of the heads of subexpressions:

The structure "Heads" gives a tree representing the same data as "HeadTrees", but with subtrees containing the heads of subexpressions themselves:

ExpressionTree[expr,"Heads"] gives output similar to TreeForm[expr]:

The structure "Subexpressions" gives a tree with the same shape as the one given by "Heads", but with data containing the subexpressions themselves rather than their heads:

The subtrees of the tree on level n correspond to the parts of the expression on level n, excluding heads:

Include heads:

The structure "Atoms" gives a tree with the same shape as the one given by "Subexpressions", but storing data only in the leaf nodes:

The structure Null gives a tree with the same shape but no data:

Construct a tree from the heads in an expression:

Use TreeFold to insert a parent node above each subtree:

This corresponds to mapping on the arguments in an expression:

Map maps on the arguments in an expression by default:

Construct a tree from the atoms in an expression:

Use TreeFold to insert a sibling node before each subtree:

This corresponds to mapping on the subexpressions in an expression:

Map maps on the subexpressions in an expression with HeadsTrue:

Construct a tree from the heads in an expression:

TreeMap maps on the data of subtrees in a tree:

This corresponds to mapping on the heads and leaves in an expression:

Map can map on the heads and leaves directly:

Construct a tree from the atoms in an expression:

TreeMap can map on the data of just the leaves in a tree:

This corresponds to mapping on the atoms in an expression:

Map can map on the atoms in an expression directly:

Depth[expr] is equivalent to TreeDepth[ExpressionTree[expr]]+1:

Depth[expr,HeadsTrue] is equivalent to TreeDepth[ExpressionTree[expr,"Subexpressions"]]+1:

ExpressionTree evaluates subexpressions before constructing the tree:

Use Unevaluated to defer evaluation of subexpressions until after the tree is constructed:

Held structures ensure that subexpressions are wrapped in HoldForm to prevent all evaluation:

Show the HoldComplete wrappers:

Construct a tree from an inactive expression: