Minimal setup for a racket language with custom syntax

This repo serves as a start project for a new racket language with a custom surface syntax. A parser generator is used to parse a very simple language of aritmetic expression only integers, +, - and grouping (..). Our sample language supports multiple aritmetic expressions defined on different lines.

Valid expressions in the language are:

1+2-(10-2)

and

4-5

and

1+2
6+7+9

but not

1.5-1

How to use it

Run in the root directory of the project

raco pkg install

After that you will be able to use

#lang sample-racket-language

at the top of your racket files. The use-language.rkt file contains a minimal example using the language defined in the repo.

Please note that the language name sample-racket-language is defined into the info.rkt file with the syntax

(define collection "sample-racket-language")

The folder structure has been created using

raco pkg new sample-racket-language

and then customizing the collection name.

Running the test suite

raco test -x -p sample-racket-language

How it works

The project leverages the parser-tools-lib package to create a parser for the sample language. The language project is built around three files:

• lexer.rkt
• parser.rkt
• main.rkt

In the lexer.rkt file we define the tokens of the language differentiating between tokens that are carrying a value with them (for example number literals), using define-tokens, and tokens that have no value (for example parenthesis), using define-empty-tokens.

In the parser.rkt we use the tokens defined in the lexer.rkt file to define our parser. The parser will return a tree describing the expression using custom functions add,multiply,subtract,divide where by custom I mean that racket doesn't provide functions nor macros with these names by default.

The main.rkt contains the required macros, the required exports and brings everything together defining the language module with a reader submodule.

(module reader racket 
    ...)

where we provide the read and read-syntax functions as required when creating a language with a custom surface syntax. The module definition part is sourced from the racket official documentation.

Resources

This is an awesome resource about macros and languages.