40 lines
1.8 KiB
Markdown
40 lines
1.8 KiB
Markdown
# Forth Interpreter in C
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A minimal Forth interpreter written in C. This project implements a subset of the Forth programming language using a threaded-code architecture with separate data and return stacks.
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## What This Is
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This is a toy/subset Forth interpreter designed for educational purposes. It provides an interactive REPL where you can define words, manipulate the stack, and execute built-in primitives.
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## How It Works
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- **Threaded Code**: The interpreter uses an inner/outer interpreter model. Colon definitions are sequences of word addresses (threaded code) traversed by an instruction pointer.
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- **Architecture**:
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- 64-bit signed integer cells (`int64_t`)
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- Separate data and return stacks
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- Fixed-size dictionary, user memory, and compile buffer
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- Dictionary is a singly-linked list searched linearly
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- **Supported Features**:
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- Stack manipulation (`DUP`, `DROP`, `SWAP`, `OVER`, `ROT`, etc.)
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- Arithmetic and logic (`+`, `-`, `*`, `/`, `MOD`, bitwise ops, comparisons)
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- Colon definitions (`: word ... ;`)
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- Variables and constants
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- Control flow (`IF ... ELSE ... THEN`, `BEGIN ... UNTIL`, `BEGIN ... WHILE ... REPEAT`)
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- Memory access (`@`, `!`, `C@`, `C!`, `HERE`, `ALLOT`)
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- Simple string output (`."`)
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- **Limitations**:
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- Fixed user memory limit (1M cells); dictionary and stacks grow dynamically
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- 64-bit signed integers only; no floating-point support
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- No file I/O or operating system interface beyond stdin/stdout
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- No immediate user-defined words or advanced introspection
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- Single-threaded execution
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- Error handling is basic (prints message and often returns zero or ignores)
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## Building
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Run `make` to build the project. The resulting binary can be run directly for an interactive Forth session.
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## Disclaimer
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This project was written with the assistance of AI. It is provided as-is for educational and experimental use.
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