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ClearAttributes

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description

ClearAttributes[s, attr]

removes attr from the list of attributes of s.

ClearAttributes[s, {attr1, attr2, ...}]

removes several attributes at a time.

ClearAttributes[{s1, s2, ...}, attrs]

removes attributes from several symbols at a time.

Examples (16)

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (12)

In[1]:= SetAttributes[f, Listable]

In[2]:= f[{1, 2, 3}]
Out[2]= {f[1], f[2], f[3]}

In[3]:= ClearAttributes[f, Listable]

In[4]:= f[{1, 2, 3}]
Out[4]= f[{1, 2, 3}]

In[5]:= SetAttributes[f, {Flat, Orderless, OneIdentity}]

In[6]:= ClearAttributes[f, OneIdentity]

In[7]:= Attributes[f]
Out[7]= {Flat, Orderless}

In[8]:= ClearAttributes[f, {Flat, Orderless}]

In[9]:= Attributes[f]
Out[9]= {}

In[10]:= SetAttributes[{g, h}, Protected]

In[11]:= ClearAttributes[{g, h}, Protected]

In[12]:= Attributes[g]
Out[12]= {}

Applications (4)

Give g an attribute to remove

In[13]:= SetAttributes[g, Orderless]

In[14]:= Attributes[g]
Out[14]= {Orderless}

Now take it away

In[15]:= ClearAttributes[g, Orderless]

In[16]:= Attributes[g]
Out[16]= {}

Implementation notes

builtin_clear_attributes (src/attr.c) clears the bitflags named in its second argument from the target symbol(s) via clear_attributes_for_symbol. The first argument may be one symbol/string or a List of them; it returns Null. ClearAttributes carries ATTR_HOLDFIRST so the symbol is not evaluated first.

  • HoldFirst, Protected.
  • ClearAttributes modifies Attributes[s].
  • Clearing an attribute that is not set is a no-op.

Attributes: HoldFirst, Protected.

References

See also: HoldFirst

Notes & additional examples

Notes

ClearAttributes[sym, attr] removes the named attribute bitflags from sym; the second argument may be a single attribute or a list of them, and the first may be one symbol or a list of symbols. It returns Null, so the two Attributes[g] queries above show the before and after.

ClearAttributes holds its first argument (HoldFirst), so the symbol is cleared rather than its value. It is the inverse of SetAttributes.