net.pelsmaeker.katerm.TermMatcher.kt Maven / Gradle / Ivy

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package net.pelsmaeker.katerm

/**
 * Matches terms.
 */
fun interface Matcher {
    /**
     * Applies the matcher to the specified term
     *
     * @return the result of the match, or `null` if the term does not match
     */
    fun match(term: I): O?


    fun  map(f: (O) -> R): Matcher = Matcher { t -> match(t)?.let(f) }
    fun filter(f: (O) -> Boolean): Matcher = Matcher { t -> match(t)?.takeIf { f(it) } }

}

//fun  Matcher.map(f: (O) -> R): Matcher = Matcher { t -> match(t)?.let(f) }
//fun  Matcher.filter(f: (O) -> Boolean): Matcher = Matcher { t -> match(t)?.takeIf { f(it) } }

object M {
    fun  id(): Matcher = Matcher { t -> t }
    fun  fail(): Matcher = Matcher { null }

    fun term(): Matcher = id()
    fun  term(m: Matcher, f: (I, O) -> R): Matcher = Matcher { t -> m.match(t)?.let { f(t, it) } }

}