Hello I just started learning Kotlin I am trying to remove d

Question

Hello I just started learning Kotlin I am trying to remove duplicates in a character mutable list I did not find appropriate idiom function to achieve this Could anyone knowledgeable about this please help var charList = a a b c c gt Expected o p a b c

Sam · Answer

My first thought would be the <https kotlinlang org api latest jvm stdlib kotlin collections distinct html|distinct> function

Sam · Answer

That will create a copy of the list I m not sure about mutating one You ll find that many of the Kotlin idioms and stdlib functions prefer immutability

CLOVIS · Answer

For naming conventions if they re in the past tense they create a new immutable value if they re in the present tense they mutate the current value ```list sort mutates list sorted immutable copy```

CLOVIS · Answer

Specifically for this case there is no efficient way to find duplicates in a `List` The efficient data structure to avoid duplicates is a `Set` ` disctint ` actually creates a `Set` adds all elements to it thus removing duplicates then creates a new `List` and adds back all elements to it Depending on what you want to do it may be a better idea to use a `Set` from the start and completely avoid `List` here

Klitos Kyriacou · Answer

Just to be a bit nerdy on naming conventions they create a new immutable value if they are adjectives Names like `sorted` are past participle adjectives Names like `distinct` are just plain vanilla adjectives

CLOVIS · Answer

Ahah thanks for the precision

ephemient · Answer

if it s a mutable collection ```charList retainAll mutableSetOf lt Char gt add ``` will remove all duplicates

CLOVIS · Answer

Wow that s more condensed that I thought possible sweat smile I didn t know it was allowed to simultaneously create an instance and use it as a method reference directly clever

ephemient · Answer

this is equivalent to ```val set = mutableSetOf lt Char gt charList retainAll set add it ``` which is equivalent to ```val set = mutableSetOf lt Char gt val iterator = charList iterator while iterator hasNext if set add iterator next iterator remove ```