BUILT-IN MATHEMATICA SYMBOL

# Apply

Apply[f, expr]
or replaces the head of expr by f.

Apply[f, expr, {1}]
or replaces heads at level of expr by f.

Apply[f, expr, levelspec]
replaces heads in parts of expr specified by levelspec.

## Details and OptionsDetails and Options

• Apply uses standard level specifications:
•  n levels through n Infinity levels through Infinity {n} level n only {n1,n2} levels through
• The default value for levelspec in Apply is .
• is equivalent to Apply[f, expr, {1}].
• A positive level n consists of all parts of expr specified by n indices.
• A negative level -n consists of all parts of expr with depth n.
• Level consists of numbers, symbols, and other objects that do not have subparts.
• Level corresponds to the whole expression.
• Apply always effectively constructs a complete new expression and then evaluates it.
• Apply operates on SparseArray objects just as it would on the corresponding ordinary lists.

## ExamplesExamplesopen allclose all

### Basic Examples (2)Basic Examples (2)

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Apply gets rid of a level of lists:

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