TagUnset
 Usage
• f/: lhs =. 去掉对lhs定义的和符号 f 关联的任何规则。
Notes
• 仅当它们的左边等于lhs并且在右边给出的Condition中的测试也相等时，去掉规则。
 Further Examples
This defines a rule for numerical values of fff and associates it with fff.
In[1]:=
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The rule applies.
In[2]:=
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Out[2]=
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The rule is undone with TagUnset.
In[3]:=
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The rule no longer applies applies.
In[4]:=
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Out[4]=
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