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

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/**
 * 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.grammar.GrammarRuleKey
import com.felipebz.flr.grammar.LexerlessGrammarBuilder
import com.felipebz.flr.grammar.LexerlessGrammarBuilder.Companion.create

/**
 * This class demonstrates how to use [LexerlessGrammarBuilder] to define grammar for simple arithmetic expressions.
 */
public enum class ExpressionGrammar : GrammarRuleKey {
    WHITESPACE, PLUS, MINUS, DIV, MUL, NUMBER, VARIABLE, LPAR, RPAR, EXPRESSION, ADDITIVE_EXPRESSION, MULTIPLICATIVE_EXPRESSION, PRIMARY, PARENS;

    public companion object {
        @JvmStatic
        public fun createGrammarBuilder(): LexerlessGrammarBuilder {
            val b = create()
            b.rule(WHITESPACE).`is`(b.commentTrivia(b.regexp("\\s*+"))).skip()
            b.rule(PLUS).`is`('+', WHITESPACE)
            b.rule(MINUS).`is`('-', WHITESPACE)
            b.rule(DIV).`is`('/', WHITESPACE)
            b.rule(MUL).`is`('*', WHITESPACE)
            b.rule(NUMBER).`is`(b.regexp("[0-9]++"), WHITESPACE)
            b.rule(VARIABLE).`is`(b.regexp("\\p{javaJavaIdentifierStart}++\\p{javaJavaIdentifierPart}*+"), WHITESPACE)
            b.rule(LPAR).`is`('(', WHITESPACE)
            b.rule(RPAR).`is`(')', WHITESPACE)
            b.rule(EXPRESSION).`is`(WHITESPACE, ADDITIVE_EXPRESSION, b.endOfInput())
            b.rule(ADDITIVE_EXPRESSION)
                .`is`(MULTIPLICATIVE_EXPRESSION, b.zeroOrMore(b.firstOf(PLUS, MINUS), MULTIPLICATIVE_EXPRESSION))
            b.rule(MULTIPLICATIVE_EXPRESSION).`is`(PRIMARY, b.zeroOrMore(b.firstOf(DIV, MUL), PRIMARY)).skipIfOneChild()
            b.rule(PRIMARY).`is`(b.firstOf(NUMBER, PARENS, VARIABLE)).skipIfOneChild()
            b.rule(PARENS).`is`(LPAR, ADDITIVE_EXPRESSION, RPAR)
            b.setRootRule(EXPRESSION)
            return b
        }
    }
}