kotlin string helpers to find index in a string where any element of another string matches first/last etc

C++ has string functions like find_first_of(), find_first_not_of(), find_last_of(),
find_last_not_of(). e.g. if I write

string s {"abcdefghi"};

• s.find_last_of("eaio") returns the index of i

• s.find_first_of("eaio") returns the index of a

  MEDevel.com: Open-source for Healthcare and Education

  Collecting and validating open-source software for healthcare, education, enterprise, development, medical imaging, medical records, and digital pathology.

  Visit Medevel

• s.find_first_not_of("eaio") returns the index of b

Does Kotlin has any equivalent.

>Solution :

Kotlin doesn’t have these exact functions, but they are all special cases of indexOfFirst and indexOfLast:

fun CharSequence.findFirstOf(chars: CharSequence) = indexOfFirst { it in chars }
fun CharSequence.findLastOf(chars: CharSequence) = indexOfLast { it in chars }
fun CharSequence.findFirstNotOf(chars: CharSequence) = indexOfFirst { it !in chars }
fun CharSequence.findLastNotOf(chars: CharSequence) = indexOfLast { it !in chars }

These will return -1 if nothing is found.

Usage:

val s = "abcdefghi"
val chars = "aeiou"
println(s.findFirstOf(chars))
println(s.findFirstNotOf(chars))
println(s.findLastOf(chars))
println(s.findLastNotOf(chars))

Output:

0
1
8
7