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Built-in Mathematica Symbol

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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.

MORE INFORMATION

form can be a pattern.

FreeQ uses standard level specifications:

	n	levels 1 through n
	Infinity	levels 1 through Infinity
	{n}	level n only
	{n₁,n₂}	levels n₁ through n₂

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 -1 consists of numbers, symbols and other objects that do not have subparts.

Level 0 corresponds to the whole expression.

With the default option setting Heads->True, FreeQ looks at heads of expressions, and their parts.

Basic Examples (2)

Test whether a list is free of 0:

FreeQ normally tests all levels in an expression:

Applications (2)

MemberQ Count StringFreeQ

Testing and Searching List Elements

Manipulating Expressions like Lists

Putting Constraints on Patterns

Elements of Lists

Expressions

Pattern Matching Functions

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