Citron > Generating the parser

Generating the parser

To generate the Swift parser code from the input grammar file, we should:

• Get a compiled version of Citron
• Run Citron on the grammar

That would create a Swift file containing the parser class.

Citron source code

The Citron source code is just three files:

1. citron.c: The Citron parser generator in C. This contains the code to generate a parser class in Swift that implements the CitronParser protocol.

2. CitronParser.swift: This file defines the CitronParser protocol, which declares placeholders for the parser tables and implements parser methods that can work on the declared tables.

3. CitronLexer.swift: This file defines the CitronLexer class, which can be used to generate the input for the parser.

While compiling our Swift code that uses the parsing interface, we should compile the following along with that:

• The generated parser
• CitronParser.swift
• CitronLexer.swift, if we’re using the lexer

Compiling Citron

To get a compiled version of Citron, we can run:

clang Sources/citron/main.c -o citron

Running Citron

To run Citron on an input grammar file called “grammar.y”, we can run:

citron grammar.y

which will generate an output file called grammar.swift. We can change the output filename with the -o switch:

citron grammar.y -o Parser.swift