forth-interpreter

A Forth language interpreter implemented in Javascript.

Installation

Clone this repo and run npm install.

Usage

Start the interpreter: npm start

Start the interpreter with debugging turned on: npm run debug

Test the interpreter: npm test

Supported Words

Output

• .s - print the stack

Mathematical Operations

• + - add two numbers, ex: 1 2 + => [3]
• - - subtract last num on stack from the second to last num on stack, ex: 5 1 - => [4]
• * - multiply two numbers, ex: 7 * 3 => [21]
• / - divide second to last num on stack by the last num on stack, ex: 10 5 / => [2]

Stack Manipulation

• . - pop from the top of the stack
• dup - duplicate top num on stack, ex: 3 dup => [3, 3]

Definitions

• : definitionName ...; - define a new operation, ex: : increment 1 +;

Conditionals

• if then - if statement, ex: if 1 then
• if else then - if/else statement, ex: if 1 else 2 then

Roadmap

Output

• emit - output num on top of stack as ascii characters

Mathematical Operations

• mod - modulus

Stack Manipulation

• drop - drop top num from stack
• swap - swap the top two nums on the stack

Conditionals

• = - boolean, -1 for true and 0 for false
• < - less than
• > - greater than
• and - and (bitwise)
• or - or (bitwise)
• invert - ! (bitwise)
• do loop - for loop

Memory

• variable - store a variable in memory
• constant - store an immutable variable in memory

Other

• Improve error handling to prevent crashes when user enters an invalid sequence of words

Contributing

Pull requests are welcome. Please make sure tests pass before submitting a PR.

License

ISC