2016-11-23 04:11:13 +08:00
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# ANTLR4 Language Target, Runtime for Swift
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2016-11-23 07:00:17 +08:00
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### Usage
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#### 1. Install ANTLR4
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[The getting started guide](getting-started.md) should get you started.
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#### 2. create a Swift lexer or parser
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This is pretty much the same as creating a Java lexer or parser, except you need to specify the language target, for example:
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```
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$ antlr4 -Dlanguage=Swift MyGrammar.g4
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```
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For a full list of antlr4 tool options, please visit the [tool documentation page](tool-options.md).
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#### 3. Get the Swift ANTLR runtime
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You will find Swift runtime (framework project) in
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```
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antlr4/runtime/Swift
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```
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#### 4. Example
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The example from [here](https://github.com/janyou/Antlr-Swift-Runtime/tree/master/Test)
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(1). Hello.g4
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```
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grammar Hello;
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r : 'hello' ID ;
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ID : [a-z]+ ;
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WS : [ \t\r\n]+ -> skip ;
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```
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(2). generate lexer/parser/visitor from Hello.g4 file
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```
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$ antlr4 -Dlanguage=Swift -visitor -o gen Hello.g4
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```
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in gen folder:
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```
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Hello.tokens
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HelloBaseListener.swift
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HelloBaseVisitor.swift
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HelloLexer.swift
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HelloLexer.tokens
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HelloLexerATN.swift
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HelloListener.swift
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HelloParser.swift
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HelloParserATN.swift
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HelloVisitor.swift
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```
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(3). make a custom listener
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```
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public class HelloWalker: HelloBaseListener{
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public override func enterR(_ ctx: HelloParser.RContext) {
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print( "enterR: " + ((ctx.ID()?.getText()) ?? ""))
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}
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public override func exitR(_ ctx: HelloParser.RContext) {
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print( "exitR ")
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}
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}
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```
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(4). call and run
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add TestHello.txt
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```
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hello world
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```
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run:
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```
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import Antlr4
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....
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do {
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let textFileName = "TestHello.txt"
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if let textFilePath = Bundle.main.path(forResource: textFileName, ofType: nil) {
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let lexer = HelloLexer(ANTLRFileStream(textFilePath))
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let tokens = CommonTokenStream(lexer)
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let parser = try HelloParser(tokens)
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let tree = try parser.r()
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let walker = ParseTreeWalker()
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try walker.walk(HelloWalker(),tree)
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} else {
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print("error occur: can not open \(textFileName)")
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}
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}catch ANTLRException.cannotInvokeStartRule {
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print("error occur: CannotInvokeStartRule")
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}catch ANTLRException.recognition(let e ) {
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print("error occur\(e)")
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}catch {
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print("error occur")
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}
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```
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