sf

"ShaderForth", closely following the implementation of Forth Haiku Salon, implemented in C. A Forth-like language is executed once for each pixel in an output image. The image is output on the standard output in plain PPM format.

make examples will generate a few GIF animations in the examples directory.

Features

Simple Forth-like compiler based on the Forth Haiku Salon language
Plain PPM output
Script to generate animated GIF pictures (multicore!): sfgif
All non-primitive words are inlined

Requirements

C compiler (I've used GCC but any C99 compiler should work
bash, xargs, dc, ImageMagick (convert) for sfgif

Missing features, compared to Forth Haiku Salon

dt: this implementation has no concept of time, though dt can be implemented as part of sfgif
mx, my, button, buttons: this implementation has no input handling
audio: this implementation has no audio output
sample, bwsample: this implementation has no image sampling
\: this implementation has no line comments (yet)
@, !: this implementation provides no memory access (yet)
if, else, then: this implementation is (for now) completely branchless
No alpha channel
Word names and numbers are limited to 31 characters each. Names and numbers longer than this may be used, but will be truncated

Additional features

width, height: Set the output image height/width. The program is executed once with its other output discarded just to retreive these values if set. If they are not set, the default of 256x256 is used.

Development

A brief description of the modules:

codebuf: A growable buffer that holds instructions
compiler: Sets up a tokenizer and handles the tokens one by one, compiling them to the virtual machine
instruction: The instruction type and the code that runs when it is executed
machine: contains two codebufs, two stacks and a small scratch memory. One data stack and one "return stack" (which isn't actually a return stack in Forth Haiku Salon and can be used across word boundaries); one main codebuf and one macro codebuf that holds compiled words
readfile: function to read a file by filename, allocating space for it and returning the data, leaving it for the caller to free
stack: Simple fixed size stack which can be used for push/pop operations
std: Standard library of primitive words
tokenizer: Simple tokenizer, the only real concern is to output words separated by whitespace one by one
types: Some of the types are interdependent, so most types relating to the virtual machine are stored here
wordlink: a simple linked list dictionary. This is used by the compiler to look up word names
sf: Main program, sets up the virtual machine, handles arguments etc.

TODO

Compilation, runtime error output with line numbers
Implement \ line comments
Implement @ and ! as in ForthSalon
(Maybe) implement IF ... ELSE ... THEN, though I like keeping it branchless
(Maybe) implement random