dynamically create kotlin variable

Question

I want to generate combinations of a string with iterable multiplication.I am try to get combination of string passed to my function.I am passing numbers and get combination of strings like 1 for abc,2 for def

fun generatexCombinations(valuePassed:String){


        val list2 = listOf("A", "B", "C")
        val list3 = listOf("D", "E", "F")
        val list4 = listOf("G", "H", "I")
        val list5 = listOf("J", "K", "L")
        val list6 = listOf("M", "N", "O")
        val list7 = listOf("P", "Q", "R", "S")
        val list8 = listOf("T", "U", "V")
        val list9 = listOf("W", "X", "Y", "Z")


        val listCombination=  mutableListOf<List<String>>()

        val charArray= valuePassed.toCharArray()
        for (char in charArray){
            when(char.toString()){
                "2"->listCombination.add(list2)
                "3"->listCombination.add(list3)
                "4"->listCombination.add(list4)
                "5"->listCombination.add(list5)
                "6"->listCombination.add(list6)
                "7"->listCombination.add(list7)
                "8"->listCombination.add(list8)
                "9"->listCombination.add(list9)
            }
        }





        //this is example of text "biryani"
        val combinationOfStrings= list2 * list4*list7*list9*list2*list6*list4

        //i want to generate above list to multiplied 
        // dynamically accroding to string value passed



    }

how can i achieve it?

i am using iterable multiplication ,please refer website below

https://www.kotlinresources.com/library/kotlindiscretemathtoolkit/

Don't convert the chars to Strings. You can use char literals: '2' -> ... — Aloso
– Aloso, Commented Nov 11, 2019 at 11:34
ok.can you tell me how it should be done? i mean dynamic generation — Akash kv
– Akash kv, Commented Nov 11, 2019 at 11:48
Your example code only uses numeral characters from the valuePassed String, but your example text "biryani" is a String composed entirely of letters. Also, if you evaluated combinationOfStrings, it would be some crazy type like a List<Triple<Triple<String, String, String>, String, String>, String, String>, which I can't imagine would be very useful. Can you explain more clearly what you want? — Tenfour04
– Tenfour04, Commented Nov 11, 2019 at 14:34
Basically, what is the input (a word or a phone number?), and what is the end result supposed to be (a list of all possible words that match a word on a phone dial?)? — Tenfour04
– Tenfour04, Commented Nov 11, 2019 at 14:39
input given is just number. if we type 23 then i have to create all thecombination of abc and def . if i type 234 then i have to give all the 3 letter combination of abc def ghi in order. kotlinresources.com/library/kotlindiscretemathtoolkit i have used this extnetion from above link — Akash kv
– Akash kv, Commented Nov 13, 2019 at 3:48

Aloso · Accepted Answer · 2019-11-11 13:03:30Z

1

Variables can't be created dynamically. They have to be known at compile-time.

Depending on the situation, you can use arrays/lists or maps instead.

Here's a solution:

//                       0   1     2      3      4      5      6      7       8      9
private val lut = listOf("", "", "ABC", "DEF", "GHI", "JKL", "MNO", "PQRS", "TUV", "WXYZ")
        .map(String::toList)

fun generateXCombinations(numericString: String) = numericString
        .filter(Char::isDigit)
        .map { lut[it - '0'] }
        .fold(listOf("")) { acc, list ->
            val pairs = acc * list
            pairs.map { (str, char) -> str + char }
        }

EDIT: I included the library and tested it. This code creates a list of strings. Each string is one possible input on the number keyboard.

edited Nov 11, 2019 at 13:03

answered Nov 11, 2019 at 11:56

Aloso

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2 Comments

Akash kv Over a year ago

i have a list of products. there is search option. user have number keyboard with abc def format on it. when user presss button 2 and 3 i have to find combination of abc and def

Akash kv Over a year ago

please check link for * operator i have used

Alexey Romanov · Accepted Answer · 2019-11-11 14:08:19Z

1

First, let's simplify building listCombination:

val mapOfLists = mapOf(
    '2' to listOf("A", "B", "C"),
    '3' to listOf("D", "E", "F"), 
    ...)

val charArray= valuePassed.toCharArray()
val listCombination = charArray.map { mapOfLists[it] }.filterNotNull()

Or charArray.map { mapOfLists[it]!! } if you are certain charArray won't contain characters for which you don't have a corresponding list. And then it's just

val combinationOfStrings = listCombination.reduce(List::times)

edited Nov 11, 2019 at 14:08

answered Nov 11, 2019 at 13:44

Alexey Romanov

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4 Comments

Tenfour04 Over a year ago

I don't think you can call mapNotNull on a primitive array.

Alexey Romanov Over a year ago

Yes, mapNotNull doesn't have these overloads, map does (kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/…). Thanks.

Akash kv Over a year ago

i have problem after creating listcombination. how can i multiply all those list inside list combination together

Alexey Romanov Over a year ago

The last line does that.

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