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Lookup

Status: Stable

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

Description

Lookup[assoc, key]
    Gives the value for key, or Missing["KeyAbsent", key].
Lookup[assoc, key, default]
    Uses default when key is absent.
Lookup[assoc, {k1, k2, ...}]
    Looks up several keys at once (O(n+m)).

Examples

All examples below are verified against the current Mathilda build.

In[1]:= Lookup[<|"a" -> 1, "b" -> 2|>, "b"]
Out[1]= 2

In[2]:= Lookup[<|"a" -> 1|>, "z", 0]
Out[2]= 0

In[3]:= Lookup[{<|"a" -> 1, "b" -> 2|>, <|"a" -> 3|>}, "a", 0]
Out[3]= {1, 3}

Implementation notes

Attributes: Protected.

Implementation status

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

References