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FreeQ

Usage

• 如果在expr中没有任何表达式匹配formFreeQ[expr, form]产生True 否则产生False
FreeQ[expr, form, levelspec]仅测试在expr的那些由levelspec指定的层的部分。


Notes

form 可以是一个模式.
• 例如: FreeQ[f[x^2] + y^2, x^_]LongRightArrow .
FreeQ 察看原始表达式的头,测试这些头是否匹配form.
• 参见 Mathematica 全书: 1.8.5节, 2.1.5节 and 2.3.5节.
• 同时参见: MemberQ, Count.
Further Examples

(同时参见 the Further Examples for the Heads option.)

This example shows a feature of FreeQ that is absent from MemberQ: here, FreeQ recognizes that the sum a+c is a subexpression of the larger sum.

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Here we see how the level argument to FreeQ affects its result. When no level is specified, matches at any level are reported.

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