Pattern Matching with Associations

Version 11 introduces several functions to simplify the manipulation and pattern matching of associations.

Use KeyMemberQ and KeyFreeQ to test whether or not a key is part of an association.

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KeyMemberQ[<|a -> 1, b -> 2, c -> 3|>, a]

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KeyFreeQ[<|a -> 1, b -> 2, c -> 3|>, a]

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KeyValuePattern allows you to match a complete association that contains one or more given rules.

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MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[b -> _]]

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MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[{c -> _, a -> _}]]

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Compute data on the gravitational field at several points of the Earth.

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points = {{40, -100, 691}, {30, -120, 560}, {80, 70, 91}}; data = GeogravityModelData /@ points

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Select the cases for which the field magnitude is larger than the standard average value.

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Cases[data, KeyValuePattern[ "Magnitude" -> _?(GreaterThan[ Quantity[1, "StandardAccelerationOfGravity"]])]]

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Use KeyValueMap to further process each key-value pair.

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Cases[data, KeyValuePattern[ "Magnitude" -> _?(GreaterThan[ Quantity[1, "StandardAccelerationOfGravity"]])]]; KeyValueMap[ EntityProperty["GeogravityModel", #1] -> UnitConvert[#2, "Imperial"] &, First[%]]

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