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 (3)¶
Every input below was run against the current Mathilda build and its output recorded.
Basic examples (3)¶
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.
References¶
- Source:
src/assoc.c - Specification:
docs/spec/builtins/data-structures.md - Tests:
tests/test_association.c - Tests:
tests/test_compile_assoc.c - Tests:
tests/test_compile_linalg.c - Tests:
tests/test_compile_transforms.c