Moved to lue-bird/elm-keysset
Β
KeysDict
Have many keys to lookup values.
Let's compare
normal Dict
You want the value where the key is
1?
0 : π‘
--> 1 : π
2 : π
the key is unique among all items
Going through while comparing your key.
the value is π where the key is `1`
KeysDict
First of all, get used to some names
- a "house" contains aspects that make it unique & aspects that can be shared across all houses
keepInParserPipelineOperator=
{ operator= "|=" --only one operator should have this symbol!
, origin= ElmRepoPackage "parser" --is the same for |.
}- a "door" describes a unique aspect across all houses.
door .operator
--is a promise, that the operator value is never the same for two houses.So... If you have a key and the type of door it could match, you can find the only matching house and enter.
You want to enter the house where
ποΈis1?
π= 0, π = π, ποΈ= 2
π= 2, π = π‘, ποΈ= 0
π= 1, π = π, ποΈ= 1 <--
π, ποΈ: doors you can "open" with a key unique across all houses
Going through while checking every house, if the
ποΈmatches.
π= 1, π = π, ποΈ= 1 where ποΈ is 1
You want to enter the house where
πis0?
--> π= 0, π = π, ποΈ= 2
π= 2, π = π‘, ποΈ= 0
π= 1, π = π, ποΈ= 1
π, ποΈ: doors you can "open" with a key unique across all houses
Going through while checking every house, if the
πmatches.
π= 0, π = π, ποΈ= 2 where π is 0
Β
π How to KeysDict
Try the ellie for some examples (always a version behind).
Example: cased letters
type alias CasedLetter=
{ lowercase: Char
, uppercase: Char
}
lowerUppercaseLetters: KeysDict CasedLetter
lowerUppercaseLetters=
KeysDict.enterableBy
[ door .lowercase, door .uppercase ]
|>putUp { lowercase= 'a', uppercase= 'A' }
|>putUp { lowercase= 'b', uppercase= 'B' }
|>putUp { lowercase= 'c', uppercase= 'C' }
uppercase char=
lowerUppercaseLetters
|>enterBy { door= .lowercase, key= char }
|>Maybe.map .uppercase
A word on imports
It's recommended to
import KeysDict.Uniqueness exposing (door)
import KeysDict exposing
( KeysDict
, houses, enterBy
, putUp, tearDown
, foldHouses, countHouses --only if you use them
)They avoid clutter and shouldn't cause name conflicts.
Example: periodic table
type Element=
Hydrogen
| Helium
elementAtomicNumberKeysDict=
KeysDict.enterableBy
[ door .atomicNumber, door .element ]
|>putUp { element= Hydrogen, atomicNumber= 1 }
|>putUp { element= Helium, atomicNumber= 2 }
atomicNumberByElement=
KeysDict.toDict { key= .element, value= .atomicNumber }
elementAtomicNumberKeysDictExample: brackets
brackets=
KeysDict.enterableBy
[ door .opening, door .closing ]
|>putUp { opening= '(', closing= ')' }
|>putUp { opening= '{', closing= '}' }
typeChar character=
case access { door= .open, key= character } brackets of
Just { closed }->
String.fromValues [ character, closed ]
Nothing->
case access { door= .closed, key= character } brackets of
Just { open }->
String.fromValues [ open, character ]
Nothing->
String.fromChar character
"Typing (: " ++(typeChar '(') ++". Even }: " ++(typeChar '}')Β
π How not to KeysDict
Example: automatic answers
answers=
KeysDict.enterableBy [ door .youSay ]
|>putUp { youSay= "Hi", answer= "Hi there!" }
|>putUp { youSay= "Bye", answer= "Ok, have a nice day and spread some love." }
|>putUp { youSay= "How are you", answer= "I don't have feelings :(" }
|>putUp
{ youSay= "Are you a robot"
, answer= "I think the most human answer is 'Haha... yes'"
}Please use a Dict where it is more appropriate: Dicts are for one-way access.
Example: translation, synonymes...
englishGerman=
KeysDict.enterableBy []
|>putIn { english= "elm", german= "Ulme" }
|>putIn { english= "git", german= "Schwachkopf" }
|>putIn { german= "RΓΌste", english= "elm" }A KeysDict is only effective, when there is only one unique key for each door.
Please take a look at elm-bidict instead!
Example: partners, opposites...
Similar to the previous example:
partners=
KeysDict.enterableBy
[ door .partner, door .partnerOfPartner ]
|>putUp { partner= "Ann", partnerOfPartner= "Alan" }
|>putUp { partner= "Alex", partnerOfPartner= "Alastair" }
|>putUp { partner= "Alan", partnerOfPartner= "Ann" }
--wait, this is no duplicate and is insertedA KeysDict ony makes sense, when the keys describe something different.
