BUILT-IN MATHEMATICA SYMBOL

# Level

Level[expr, levelspec]
gives a list of all subexpressions of expr on levels specified by levelspec.

Level[expr, levelspec, f]
applies f to the sequence of subexpressions.

## Details and OptionsDetails and Options

• Level uses standard level specifications:
•  n levels 1 through Infinity levels 1 through Infinity {n} level only {n1,n2} levels through
• Level[expr, {-1}] gives a list of all "atomic" objects in expr.
• A positive level consists of all parts of expr specified by indices.
• A negative level consists of all parts of expr with depth .
• Level 0 corresponds to the whole expression.
• With the option setting , Level includes heads of expressions and their parts.
• Level traverses expressions in depth-first order, so that the subexpressions in the final list are ordered lexicographically by their indices.

## ExamplesExamplesopen allclose all

### Basic Examples (3)Basic Examples (3)

Give all parts at level -1:

 Out[1]=

Give all parts down to level 2:

 Out[1]=

Give all parts at levels 0 through infinity:

 Out[1]=