ParserInput

class ParserInput<out I : Any, U : Any>(val input: List<I>, val index: Int, val userContext: U)

An immutable, position-aware view into a token sequence, optionally carrying a user-defined context value.

Every successful parse step produces a new ParserInput advanced past the consumed tokens; the underlying input list and userContext are shared by reference, so advancing is allocation-light.

Type parameters

I — the token type (e.g. Char). Covariant: a ParserInput<Char, U> can be read wherever a ParserInput<Any, U> is expected.
U — the user context type. Invariant. Use Unit when no context is needed.

Example

data class ParseState(val source: String)

val input = ParserInput.of("hello".toList(), ParseState("hello.kt"))
println(input.current())   // 'h'
println(input.advance().current())  // 'e'
println(input.userContext.source)   // "hello.kt"