連想を使ったパターンマッチング
バージョン11では,連想の操作とパターンマッチングを簡単にするいくつかの関数が導入されている.
KeyMemberQおよびKeyFreeQを使ってキーが連想の一部かどうかを調べる.
In[1]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_72.png)
KeyMemberQ[<|a -> 1, b -> 2, c -> 3|>, a]
Out[1]=
![](assets.ja/pattern-matching-with-associations/O_75.png)
In[2]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_73.png)
KeyFreeQ[<|a -> 1, b -> 2, c -> 3|>, a]
Out[2]=
![](assets.ja/pattern-matching-with-associations/O_76.png)
KeyValuePatternを使うと,指定された規則を1つあるいは複数含む連想全体をマッチすることができる.
In[3]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_74.png)
MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[b -> _]]
Out[3]=
![](assets.ja/pattern-matching-with-associations/O_77.png)
In[4]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_75.png)
MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[{c -> _, a -> _}]]
Out[4]=
![](assets.ja/pattern-matching-with-associations/O_78.png)
地球上のいくつかの点における重力場についてのデータを計算する.
In[5]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_76.png)
points = {{40, -100, 691}, {30, -120, 560}, {80, 70, 91}};
data = GeogravityModelData /@ points
Out[5]=
![](assets.ja/pattern-matching-with-associations/O_79.png)
重力場の値が標準平均値よりも大きくなる場合をいくつか選ぶ.
In[6]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_77.png)
Cases[data,
KeyValuePattern[
"Magnitude" -> _?(GreaterThan[
Quantity[1, "StandardAccelerationOfGravity"]])]]
Out[6]=
![](assets.ja/pattern-matching-with-associations/O_80.png)
KeyValueMapを使ってキーと値の各ペアをさらに処理する.
In[7]:=
![Click for copyable input](assets.ja/pattern-matching-with-associations/In_78.png)
Cases[data,
KeyValuePattern[
"Magnitude" -> _?(GreaterThan[
Quantity[1, "StandardAccelerationOfGravity"]])]];
KeyValueMap[
EntityProperty["GeogravityModel", #1] ->
UnitConvert[#2, "Imperial"] &, First[%]]
Out[7]=
![](assets.ja/pattern-matching-with-associations/O_81.png)