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Discussion on: From Java to Kotlin in 20 minutes ⚡️

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jmfayard profile image
Jean-Michel Fayard 🇫🇷🇩🇪🇬🇧🇪🇸🇨🇴 Author • Edited

Thanks a lot for your comment, this article was fun to write but I had no idea if it would be useful.
Fold() can be used for example to reimplement the sum of elements in a list. You give it an initial value (0), and a function that you apply to an accumulator (your sum so far) and each next element

fun main() {
    val ints = listOf(1, 4, 6, 8, 13)
    val sum = ints.fold(0) { sum, elem -> sum + elem }
    println(sum) // 32
}
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See pl.kotl.in/5WMtht8FA

Before we treated what happened if you had 0, 1 or more than 1 element. Instead we could handle the case with 0 elements or more than 0. Next step was to use fold().

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abhinav1217 profile image
Abhinav Kulshreshtha

Ok, So isEmpty check is replaced by having an initial value as parameter of fold. case for 1 or more is handled by lambda. I think I understand it now. So those check-steps are not needed anymore.

acc will be initialized as empty setOf string because that is what is passed inside fold(), c will be current iterated value. and then you call combineSolutions with acc and mapPin of c.

Man lambdas are trippy.

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jmfayard profile image
Jean-Michel Fayard 🇫🇷🇩🇪🇬🇧🇪🇸🇨🇴 Author

Exactly 👏🏻