Forther

A forth like langauge. When I started working on this I had no idea about Forth. The only thing I knew was that I knew that it was stack-based.

This is why many of the implementations are much different than what would you expect from a forth implementation. This is also one reason as to why we have different types on the stack (such as stacks, strings, words, exact (int) and inexact (double) numbers).

Syntax

Values

You can add any values to the stack like this:

1 2.3 "4" five false { 6 7.8 "9" ten }

This will add:

1. an Exact with value 1.
2. an Inexact with value 2.3.
3. a String with value "4".
4. a Word with value :five.
5. a Boolean with value false.
6. a List / Stack with value { 6 7.8 "9" ten }.

If

To check if a number is even or not you could for example use this:

{ "even" println . } { "odd" println . } x 2 | if

The general syntax follows this:

{ if-true } { if-false } <cond> if

For

A word :I is inserted into the dictionary for each iteration with the current iteration value.

This:

{ I print ". line" println .  } 1 10 for

would print:

1. line
2. line
3. line
4. line
5. line
6. line
7. line
8. line
9. line
10. line

The general syntax follows this:

{ for-block (with :I in the dict) } from to for

Built-In words

Use the :words word to see all words. You can override any word at any time, even built-in ones.

Examples

See ./examples/*.forther for examples.

Note

Right now forther cannot read from a file, thus the shebang does not actually work yet.
Run the files like this instead:

cat ./examples/fizzbuzz.forther | forther

Current Status (incomplete)

• ✅ A basic repl
  • ✅ If
  • ✅ For
  • ✅ Basic stack operations
  • ❌ While (to have conditional looping)
• ✅ ErrorCall free (better error handling)
  • There is still improvement for error handling (Result, IO, State, ...)
  • some of the pure functions in Stack or BinTree are not total
• ✅ reading from a file
• ✅ Compile mode
• ❌ Dumping the current word list to a file
• ❌ JVM backend
• (❌) Maybe a cuomst vm?
• ❌ IO Operations / Graphs stuff for Advent of Code.

Goal

I want to solve one day of Advent of Code with this.