BUILT-IN MATHEMATICA SYMBOL

FreeQ

FreeQ[expr, form]
yields True if no subexpression in expr matches form, and yields False otherwise.

FreeQ[expr, form, levelspec]
tests only those parts of expr on levels specified by levelspec.

Details and Options Details and Options

form can be a pattern.
FreeQ 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 FreeQ is {0, Infinity}.
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.
With the default option setting Heads->True, FreeQ looks at heads of expressions, and their parts.