README

Attempt at writing a Forth interpreter from scratch, with SDL2 integration for hacking away at small games. I am aware that having resizable hash tables is overkill for a Forth. This is really just to learn to write an interpreter for what is probably the easiest language to interpret. I hope for this to be a stepping stone to writing something like a Scheme interpreter, as well as having an excuse to write some data structures in C.

Reference Material:
Easy Forth
Starting Forth
Forth C Implementation
VM Stuff
Forth Fundamentals
Thinking Forth

Example

Keys: SWAP, *, +, -, ., /, DROP, <, =, >, DUP, 
> : ZERO? 0 = IF 13 . THEN ;
STACK: 
VM: [0: 0][1: EQUALS][2: BRANCH(5)][3: 13][4: DOT][5: RET]
> 0 ZERO?
13
STACK: 
VM: [0: 0][1: EQUALS][2: BRANCH(5)][3: 13][4: DOT][5: RET][6: 0][7: JMP(0)]

TODO:

• implement "ELSE"
• add strings (disallow spaces for simplicity)

Add more builtins

• =
• >
• <
• OVER
• ROT
• MOD
• /MOD

Tests

• stack
• vm
• improve error handling

Read Starting Forth Ch 4 https://www.forth.com/starting-forth/4-conditional-if-then-statements/

Control flow/storage

• implement variables
• constants
• implement cells
• implement begin until
• implement input handling

Cleanup n stuff

• read multiple lines
• read files
• add all built-ins
• improve the way of initializing the built-ins table
• add case-insensitivity