SwiftParse is a parser combinator library. This project is still iterating rapidly and is not stable.
Let's build a parser for the brainfuck language. It's a terrible language but makes for a nice example of how to use SwiftParse.
import SwiftParse
enum Instruction {
case incPointer, decPointer, incByte, decByte, writeByte, readByte
case loop([Instruction])
}
typealias LoopParser = StandardParser<String, Instruction>
struct BrainfuckParser {
static let incPointer = match(">") ^^ { _ in Instruction.incPointer }
static let decPointer = match("<") ^^ { _ in Instruction.decPointer }
static let incByte = match("+") ^^ { _ in Instruction.incByte }
static let decByte = match("-") ^^ { _ in Instruction.decByte }
static let writeByte = match(".") ^^ { _ in Instruction.writeByte }
static let readByte = match(",") ^^ { _ in Instruction.readByte }
static let pointerOps = incPointer | decPointer
static let byteOps = incByte | decByte
static let ioOps = writeByte | readByte
static let operation = pointerOps | byteOps | ioOps | loop()
// loop must defined as a static function because it references
// operation which in turn references loop.
static let loop: () -> LoopParser = {
loopStart ~ operation* ~ loopEnd ^^ { Instruction.loop($0.0.1) }
}
static let loopStart = match("[")
static let loopEnd = match("]")
static let program = operation+
}Now let's execute it and see what it parsed:
let result = BrainfuckParser.program(AnyCollection("+[>,]"))
let parseTree = try! result.get().valueThis generates a parse tree of:
[
SwiftParse.Brainfuck.incByte,
SwiftParse.Brainfuck.loop([
SwiftParse.Brainfuck.incPointer,
SwiftParse.Brainfuck.readByte
])
]And no unparsed characters left over. Neat!
For more complete examples check out https://github.com/mgadda/swift-parse-examples