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Interpreter framework for Lisp-based extension and scripting languages on macOS. LispKit is based on the R7RS standard for Scheme. Its compiler generates bytecode for a virtual machine. LispKit is fully implemented in Swift 5.

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README.md

LispKit Swift LispKit

Platform: macOS Language: Swift 5.3 IDE: Xcode 12.1 Carthage: compatible License: Apache

Overview

LispKit is a framework for building Lisp-based extension and scripting languages for macOS applications. LispKit is fully written in the programming language Swift. LispKit implements a core language based on the R7RS (small) Scheme standard. It is extensible, allowing the inclusion of new native libraries written in Swift, of new libraries written in Scheme, as well as custom modifications of the core environment consisting of a compiler, a virtual machine as well as the core libraries.

So far, performance was not a priority in the development of LispKit. The LispKit compiler does not perform many code optimizations and the performance of the system is below state of the art Lisp and Scheme implementations.

The NumericalScheme demo showcases how to create a derived LispKit interpreter that inherits everything from LispKit (without code duplication) and defines a new native as well as Scheme-based library.

LispPad implements a simple, lightweight, integrated development environment for LispKit on macOS with a Cocoa-based UI. The LispPad Library Reference documents the core LispPad and LispKit libraries in PDF form. A simpler command-line tool with similar functionality is provided by the LispKit framework itself (see below).

Features

LispKit provides support for the following core features, many of which are based on R7RS:

LispKit is incompatible or incomplete with respect to the following R7RS features:

  • Lists are immutable. Mutable cons-cells are supported in a way similar to Racket
  • Literals in syntax-rules are not matched based on their definition but their symbol identity
  • Datum comments introduced via #; do not always work as in other Scheme dialects.

The following SRFI libraries have been ported to LispKit and are included in the framework:

Project

The project defines three different targets:

  • LispKit: the core interpreter framework, including all support files
  • LispKitTools: a framework for tools supporting LispKit; e.g. a read-eval-print framework
  • LispKitRepl: a command-line tool implementing a read-eval-print loop

Architecture

From an architectural perspective, LispKit consists of:

  1. a compiler translating LispKit expressions into bytecode,
  2. a virtual machine for interpreting the generated bytecode. The virtual machine is stack-based, handles tail calls and continuations, and provides a garbage collector.
  3. a large range of libraries, all packaged together with the framework.

Details can be found in the LispKit Wiki.

Command-line tool

Overview

This project also includes a command-line tool, called the LispKit Shell, for executing LispKit applications in the terminal. It can be used to try out and experiment with the LispKit framework. The command-line tool can also be used interactively as a read-eval-print loop. The read-eval-print loop parses the entered LispKit expression, compiles it to bytecode, executes it, and displays the result.

Downloading the source code

First, clone the LispKit repository via git. The following command will create a directory swift-lispkit.

> git clone https://github.com/objecthub/swift-lispkit.git
Cloning into 'swift-lispkit'...
remote: Enumerating objects: 14, done.
remote: Counting objects: 100% (14/14), done.
remote: Compressing objects: 100% (12/12), done.
remote: Total 5300 (delta 1), reused 14 (delta 1), pack-reused 5286
Receiving objects: 100% (5300/5300), 1.76 MiB | 132.00 KiB/s, done.
Resolving deltas: 100% (3724/3724), done.

Next, switch to Xcode and build the LispKit command-line tool via scheme LispKitRepl:

> open LispKit.xcodeproj

Compiling the command-line tool with the Swift Package Manager

A debug binary can be built in the following way:

> cd swift-lispkit
> swift build -Xswiftc "-D" -Xswiftc "SPM"
Fetching https://github.com/objecthub/swift-numberkit.git
Fetching https://github.com/objecthub/swift-commandlinekit.git
Fetching https://github.com/objecthub/swift-markdownkit.git
Completed resolution in 6.47s
Cloning https://github.com/objecthub/swift-numberkit.git
Resolving https://github.com/objecthub/swift-numberkit.git at 2.3.2
Cloning https://github.com/objecthub/swift-markdownkit.git
Resolving https://github.com/objecthub/swift-markdownkit.git at 0.2.0
Cloning https://github.com/objecthub/swift-commandlinekit.git
Resolving https://github.com/objecthub/swift-commandlinekit.git at 0.3.1
[124/124] Linking LispKitRepl

The debug binary can be run by invoking .build/debug/LispKitRepl -d LispKit assuming that directory ~/Documents/LispKit contains a copy of the resources directory needed to run the command-line tool.

A release binary can be built like this:

> cd swift-lispkit
> swift build -c release -Xswiftc "-D" -Xswiftc "SPM"
Fetching https://github.com/objecthub/swift-numberkit.git
Fetching https://github.com/objecthub/swift-commandlinekit.git
Fetching https://github.com/objecthub/swift-markdownkit.git
Completed resolution in 4.02s
Cloning https://github.com/objecthub/swift-numberkit.git
Resolving https://github.com/objecthub/swift-numberkit.git at 2.3.2
Cloning https://github.com/objecthub/swift-markdownkit.git
Resolving https://github.com/objecthub/swift-markdownkit.git at 0.2.0
Cloning https://github.com/objecthub/swift-commandlinekit.git
Resolving https://github.com/objecthub/swift-commandlinekit.git at 0.3.1
[6/6] Linking LispKitRepl

The release binary can be run by invoking .build/release/LispKitRepl -r Sources/LispKit/Resources in the directory swift-lispkit (in which the binary was build above).

Assuming that directory ~/Documents/LispKit contains a copy of the resources directory, it is also possible to run the release binary by invoking .build/release/LispKitRepl -d LispKit.

Requirements

The following technologies are needed to build the components of the LispKit framework. For building the command-line tool, all that is needed is the Swift Package Manager. For compiling the framework and trying the command-line tool directly in Xcode, the Swift Package Manager is not needed.

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Interpreter framework for Lisp-based extension and scripting languages on macOS. LispKit is based on the R7RS standard for Scheme. Its compiler generates bytecode for a virtual machine. LispKit is fully implemented in Swift 5.

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