AzimMuradov/kpeg

Welcome to the Kotlin PEG parser with Kotlin DSL!

The project is inspired by the pest parser and the kotlin-peg-dsl project.

Quick start

Simple example

val num = Symbol.rule<Int>(name = "Num", ignoreWS = false) {
    seq {
        val sign = +char('+', '-').orDefault('+')
        val digits = +DIGIT.oneOrMore().joinToString()

        value { (sign.get + digits.get).toInt() }
    }
}

val sum = Symbol.rule<Int>(name = "Sum") {
    num.list(separator = char('+'), min = 1u).mapPe { it.sum() }
}


fun evalExpr(expression: String) =
    PegParser.parse(symbol = sum.value(), expression).getOrElse { null }

val results = listOf(
    evalExpr("1"),                         // 1
    evalExpr("+1"),                        // 1
    evalExpr("+ 1"),                       // null
    evalExpr("+1 +"),                      // null
    evalExpr("-17"),                       // -17
    evalExpr("-1 7"),                      // null
    evalExpr("1+2+3+4+5"),                 // 15
    evalExpr("1 + +2 + -3 + +4 + 5"),      // 9
    evalExpr("definitely not expression"), // null
    evalExpr(""),                          // null
)

for (res in results) {
    println(res)
}

Resources

Documentation
Examples
- Simple calculator
- Json parser
About PEG
PEG formal description
Other useful papers

Installation guide

Gradle

Kotlin DSL

dependencies {
    implementation("io.kpeg:kpeg:0.1.2")
}

Groovy DSL

dependencies {
    implementation 'io.kpeg:kpeg:0.1.2'
}

Maven

<dependency>
    <groupId>io.kpeg</groupId>
    <artifactId>kpeg</artifactId>
    <version>0.1.2</version>
</dependency>

Things to improve before stable:

add more docs
add more tests, improve the code coverage
add more built-in characters
add ability to define Comment parsing expression
better error messages and error handling
support left recursion
provide more examples
multiplatform

Suggestions are welcome!

License

kpeg is released under the Apache 2.0 license.

Copyright 2021-2021 Azim Muradov

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

AzimMuradov / kpeg