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harlowe:dataset [2017/06/19 02:36]
l created
harlowe:dataset [2017/10/09 20:39]
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-[[harlowe:​Array|Array]] are useful for dealing with a sequence of related data values, especially if 
-they have a particular order. There are occasions, however, where you don't really 
-care about the order, and instead would simply use the [[harlowe:​Array|Array]] as a storage place for 
-values - using ''​%%contains%%''​ and ''​%%is in%%''​ to check which values are inside. 
- 
-Think of datasets as being like arrays, but with specific restrictions:​ 
- 
-  * You can't access any positions within the dataset (so, for instance, the ''​%%1st%%'',​ ''​%%2ndlast%%''​ 
-and ''​%%last%%''​ aren't available, although the ''​%%length%%''​ still is) and can only use ''​%%contains%%''​ 
-and ''​%%is in%%''​ to see whether a value is inside (or, by using ''​%%any%%''​ and ''​%%all%%'',​ many values). 
-  * Datasets only contain unique values: adding the [[harlowe:​string|string]] "​Go"​ to a dataset already 
-containing "​Go"​ will do nothing. 
-  * Datasets are considered equal (by the ''​%%is%%''​ operator) if they have the same items, regardless 
-of order (as they have no order). 
- 
-These restrictions can be helpful in that they can stop programming mistakes from 
-occurring - you might accidentally try to modify a position in an array, but type the name of 
-a different array that should not be modified as such. Using a dataset for the second 
-array, if that is what best suits it, will cause an error to occur instead of allowing 
-this unintended operation to continue. 
- 
-^Operator ​       ^ Meaning ^ Example ^ 
-| ''​is''​ | Evaluates to boolean ''​true''​ if both sides contain equal items, otherwise ''​false''​. | ''​(ds:​1,​2) is (ds 2,​1)''​ (is true)| 
-| ''​is not''​ | Evaluates to ''​true''​ if both sides differ in items. | ''​(ds:​5,​4) is not (ds:​5)''​ (is true)| 
-| ''​contains''​ | Evaluates to ''​true''​ if the left side contains the right side. | ''​(ds:"​Ape"​) contains "​Ape"'',​ ''​(ds:​(ds:​99)) contains (ds:​99)'',​ ''​(ds:​ 1,2,3) contains all of (a:​2,​3)'',​ ''​(ds:​ 1,2,3) contains any of (a:​3,​4)''​| 
-| ''​is in''​ | Evaluates to ''​true''​ if the right side contains the left side. | ''"​Ape"​ is in (ds:"​Ape"​)'',​ ''​(a:​3,​4) is in (ds:​1,​2,​3)''​| 
-| ''​+''​ | Joins datasets. | ''​(ds:​1,​2,​3) + (ds:​1,​2,​4)''​ (is ''​(ds:​1,​2,​3,​4)''​)| 
-| ''​-''​ | Subtracts datasets. | ''​(ds:​1,​2,​3) - (ds:​1,​3)''​ (is ''​(ds:​2)''​)| 
-| ''​...''​ | When used in a macro call, it separates each value in the right side., The dataset'​s values are sorted before they are spread out.| ''​(a:​ 0, ...(ds:​1,​2,​3,​4),​ 5)''​ (is ''​(a:​0,​1,​2,​3,​4,​5)''​)| 
  
harlowe/dataset.txt ยท Last modified: 2017/10/09 20:39 (external edit)