Forge

Forge is a dynamically-typed language written in Rust. It is inspired by JavaScript, Rust, Python and Rhai. In the future, you'll be able to use Forge as a general-purpose lightweight scripting language in your applications.

You can try out Forge in your browser here!

Example

# A function to square numbers
var square = |x| {
	return x * x;
};

var n = input "How many squares? ";

# Create a list of squares
var squares = [];
for x in 1..n + 1 {
	squares += square(x);
}

# Iterate and print squares
for square in squares {
	print square;
}

Goals

Simple, familiar syntax
Lightweight, quick to parse
Moderately fast execution speeds
Well-considered, 'common-sense' design
Useful, informative error messages
Easy to build into an existing codebase
Python-like REPL prompt

Usage

Using Forge is similar in principle to using Python. Once compiled, running the shell or executing scripts with the interpreter is trivial. You'll need to compile the cli/ crate to gain access to the interpreter binary.

To access the REPL shell, run:

$ forge

To execute a script, run:

$ forge my_script.fg

Roadmap

Some Syntax Examples

List splicing

>> var my_list = [0, 1, 2, 3];
>> my_list[1..2]
[1]
>> my_list[1..3] = ["this", "is", "a", "list", "splice"];
>> my_list
[0, this, is, a, list, splice, 3]

String splicing

>> "Hello, world!"[7..12]
world
>> var test = "An apple is what I am eating";
>> test[3..8] = "pear";
>> test
An pear is what I am eating
>>

Design

Types

Forge has several distinct types:

Number 64-bit, floating-point
String unicode-compliant
Char unicode-compliant
Boolean
Range
Function
List
Map
Object Currently unimplemented
Custom Used to call to and from Rust
Null

Things To Do

Investigate design features that would make the dynamic type system easier to optimise

Interpreter

Currently, Forge is only implemented as an AST-walking interpreter. In the future, I aim to generate more efficient low-level bytecode for the language. I also aim to implement many a variety of optimisations throughout the compilation process.

Error Messages

Forge aims to produce the most useful, informative and intelligence error messages it can. Errors can be emitted at compile-time or run-time. Below are a few examples.

Parser errors:

[ERROR] Parsing error at 1:45...
   ...while parsing if-else statement...
   ...while parsing print statement...
        1| var x = 1; if x > 2 { print "Hello, world!" oops; }
         |                                             ^^^^
   Expected ';', found identifier 'oops'.

Runtime errors:

[ERROR] Runtime error at 1:21...
        1| var p = true; while p { print "On the next iteration, p will be null"; p = null; }
         |                     ^
   Cannot determine the truthiness of value of type 'null'. Did you mean for this to be a bool?

Runtime errors that produce error messages that reference code written during the previous declaration of a function object:

[ERROR] Runtime error at 1:10...
        1| var say_hello = || { print "Hello, world!"; };
         |                 ^^
        1| say_hello(1); # Wrong number of parameters
         |          ^^^
   Tried to call a function with the wrong number of parameters. Expected 0, found 1.

zesterer/forge