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• RecursiveGrammar.kt

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com.felipebz.flr.examples.grammars.RecursiveGrammar.kt Maven / Gradle / Ivy

/**
 * FLR
 * Copyright (C) 2010-2023 SonarSource SA
 * Copyright (C) 2021-2023 Felipe Zorzo
 * mailto:felipe AT felipezorzo DOT com DOT br
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package com.felipebz.flr.examples.grammars

import com.felipebz.flr.api.Grammar
import com.felipebz.flr.grammar.GrammarRuleKey
import com.felipebz.flr.grammar.LexerlessGrammarBuilder

/**
 * While for performance reasons preferable to write greedy rules instead of recursive,
 * impossible to avoid recursion at all.
 * Depth of recursion not limited by Java stack size (i.e. can't lead to [StackOverflowError])
 * and limited only by amount of available memory.
 */
public enum class RecursiveGrammar : GrammarRuleKey {
    S;

    public companion object {
        @JvmStatic
        public fun create(): Grammar {
            val b = LexerlessGrammarBuilder.create()
            b.rule(S).`is`("(", b.optional(S), ")")
            return b.build()
        }
    }
}