Wren Console - wrenc

The Wren Console project is a small and simple REPL and CLI tool for running Wren scripts. It is backed by libuv to implement IO functionality. It is based on the official Wren CLI project and very much a work in progress.

The goals and priorities are slightly different than the Wren CLI project.

• To be written as much as possible in pure Wren, not C. This greatly simplifies much, expands the list of potential contributors, as makes developing new features faster (for everyone who knows Wren).
• Provide the best learning environment for the forthcoming Exercism Wren track. For starters this means providing full introspection of stack traces when a Fiber aborts - allowing test suites to show helpful debugging information, including source code snippets. (thanks to @mhermier)
• Serve as a development playground for good ideas that may or may not ever make it into Wren CLI proper. If much of what we do makes it into Wren CLI, great. If we end up going different directions, that's ok too.

For now the idea is to try to maintain compatibility with whe Wren CLI modules themselves, so that reference documentation may prove useful.

For more information about Wren, the language that Wren Console is embedding, see http://wren.io.

We welcome contributions. Feel free to open an issue to start a discussion or join our Discord. You can also find me on the main Wren Discord as well.

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FAQ

Pure Wren? Why?

• It's higher level and therefore easier to read, write, and iterate than C.
• It's more than fast enough.
• I've fallen a bit in love with Wren.
• It's fun. Is there any better reason?
• Many (including myself) don't know C nearly well enough to be proficient with major CLI contributions.

Exercism?

Thousands of helpful mentors, hundreds of thousands of fellow students to learn alongside. If you're wanting to learn a new language, improve your Wren, or just sharpen your skills on an entirely different language, Exercism is the place to be.

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Usage Examples

Start up an interactive REPL session:

$ wrenc

Run a script from the console:

$ wrenc ./path_to_script.wren

Evaluate code directly:

$ wrenc -e 'System.print("Hello World!")'

Executable Wren scripts:

Use the typical "shebang" for executable wren scripts:

#!/usr/bin/env wrenc
import "io" for Stdin
System.print("Enter your name:")
var name = Stdin.readLine().trim()
System.print("Hello %(name.isEmpty ? "World" : name)!")

(Note: for Linux folk, this is documented in the execve(2) man page.)

Embed Wren code in a shell script:

This makes smart use of file descriptors and the Linux /dev file system to read the code from a here-document while also keeping standard input available for wren:

#!/bin/sh
wrenc /dev/fd/5 < input.txt 5<< 'EOF'
import "io" for Stdin
System.print(Stdin.readLine())
EOF

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Extended Library Support

Our hope is to extend the libraries available without breaking forwards compatibility - meaning that a script running successfully on Wren CLI should run as-is on Wren Console - but once you start using the newer library features your script may no longer run be backwards compatible with Wren CLI.

wren-package module

Dirt simple package management/dependencies for Wren Console projects.

• WrenPackage class
• Dependency class
• See wren-package for usage details

io module

• Stderr.write(s) - Write a string to srderr
• Stderr.print(s) - Write a string to stderr followed by a newline
• File.dirname(path) - Strip last component from file name
• File.basename(path) - Strip directory from filenames
• File.basename(path, suffixes) - Strip directory and suffix from filenames

os module

• Process.exec(command, [arguments, [workingDirectory, [environment]]]) - Run an external command and display it's output
• Process.exit() - Exit immediately with 0 status code
• Process.exit(code) - Exit immediately with the specified exit status code. (wren-lang#74)
• Process.chdir(dir) - Change the working directory of the process

ensure module

Argument validation...

• Ensure.map(v,name) - value must be Map, or abort with ArgumentError
• Ensure.list(v,name) - value must be List, or abort with ArgumentError
• Ensure.num(v,name) - value must be Num, or abort with ArgumentError
• Ensure.string(v,name) - value must be String, or abort with ArgumentError
• Ensure.bool(v,name) - value must be bool, or abort with ArgumentError
• Ensure.int(v,name) - value must be integer, or abort with ArgumentError
• Ensure.positiveNum(v,name) - value must be positive number, or abort with ArgumentError
• Ensure.positiveInt(v,name) - value must be positive integer, or abort with ArgumentError
• Ensure.fn(v, arity, name) - value must be function with arity, or abort with ArgumentError
• Ensure.type(v, type, name) - value must be of given type, or abort with ArgumentError

Example:

static sleep(milliseconds) {
  Ensure.positiveNum(milliseconds, "milliseconds")
  // ...
}  

runtime module

Retrieve details about the runtime environment.

• Runtime.NAME - The runtime name
• Runtime.VERSION - The runtime version number
• Runtime.WREN_VERSION - The Wren version the runtime is built against
• Runtime.details - retrieve additional details about the runtime environment
• Runtime.capabilities - list of supported capabilities
• Runtime.hasCapability(name) - query if specific capability is supported by runtime

mirror module

Experimental. See wren-lang/wren#1006.

• Mirror.reflect(object) - Reflect on an object
• Mirror.reflect(class) - Reflect on a class
• Mirror.reflect(fiber) - Reflect on a fiber, it's stacktrace, etc.

essentials module

Wren Console includes the Wren Essentials library built right into the binary.

• Time.now() - number of milliseconds since Epoch
• Time.highResolution() - high resolution time counter (for benchmarking, etc.)
• Strings.upcase(s) - convert an ASCII string to uppercase
• Strings.downcase(s) - convert an ASCII string to lowercase
• Strings.titlecase(s) - convert an ASCII string to "Title Case"
• Strings.capitalize(s) - capitalize first letter of an ASCII string
• Strings.globMatch(s, pattern) - glob match capabilities ported from TCL

json module

• JSON.encode(data, [options]) - encode data into JSON string
• JSON.decode(json, [options]) - decode JSON string into data
• JSON.stringify(data) - alias of encode
• JSON.parse(json) - alias of decode

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Installing

If you're using Homebrew we have a tap for you. Otherwise you can check out our binary releases or simply build from source.

With Homebrew:

brew tap exercism/wren
brew install wren-console

Building from source

Pre-requisites

• Git clone the wren-essentials project (link) into deps (TODO: vendor?)

Windows

The projects/vs20xx folders contain Visual Studio projects.

macOS

The projects/xcode folder contains an Xcode project.

The projects/make.mac folder also contains a make project.
From that folder, run make.

cd projects/make.mac
make

Linux

The projects/make folder contains a make project.
From that folder, run make.

cd projects/make
make

FreeBSD

The projects/make.bsd folder contains a make project.
From that folder, run make.

cd projects/make.bsd
gmake

Alternative build options

The projects are generated by premake, found inside projects/premake.
You can use premake5 (alpha 14 was used) to generate other projects.
Generate other system's projects via the premake --os flag,
i.e if on linux, premake vs2019 --os=windows is valid.

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