simia

Created with https://www.craiyon.com/ and manually vectorized in Figma

Go implementation of the Monkey language interpreter from the book Writing an interpreter in Go

NOTE: this repo is work in progress

Differences from Monkey

I have extended and took some different design decisions while designing the simia language:

• No nil value supported. Variables must always be defined with the supported types
• Added Range support defined by start and end integers
• Added support for in operator
• Added for-loop support with boolean or in expressions
• Parentheses are optional for if and for blocks
• Added |> operator (borrowed from elixir)

Development

See available helpers commands for development in the Makefile

Usage

Run the REPL

make run

Run the wasm example and open http://localhost:8080

make run-wasm

Syntax

Variables declaration and assignment

let foo = "";
foo = "bar";

Arithmetic expressions

let a = 13 + 9;
let b = 19 * a;
b = 7 - (b / 20) * a;

For loops

for i in 1..10 {
  log(i);
}

let i = 0;
for i < 10 {
  log(i);
  i = i + 1
}

let condition = true;
let stop = fn() { 
  condition = false;
}
for condition {
  condition = stop();
}

let ret = ""
for el in ["hello", "universe"] {
  ret = ret + el
}

For-loops have a limit of 10000 iterations. See evaluator

Pipe operator

let add = fn(x, y) { x + y };
let multiply = fn(x, y) { x * y };
let foo = 1 + 2 |> add(8) |> multiply(2)
>> foo
22

Builtin functions

• len(<iterable>): Returns length of iterable (string, array, range)
• log(...args): Prints arguments to the standard output followed by a new line
• append(array): Pushes value to the end of the array

Types

Type	Syntax
bool	true
int	0 42 1234 -5
string	"" "foo" "\"quotes\" and a\nline break"
array	[] [1, 2] [1, 2, 3]
hash	{} {"a": 1} {"a": 1, "b": 2, identifier: 0}

TODO

• Add collumn and line numbers
• Implement array with spread ... operator
• Support piping like in Elixir (|>)
• Use tinygo to reduce wasm size

License

MIT License

Copyright (c) 2022 Brian Mayo

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.