# forth.jl
-A hobby implementation of a FORTH-like system atop the Julia scientific
-computing language. It will never be useful for any purpose besides, perhaps,
-pedagogical - although I wouldn't advise trying to learn forth by using this
-code directly. A better approach is to combine reading something like Leo Brodie's
-book Starting Forth with implementing your own forth.
-
-To a large degree this project is simply a port of the literate programming
-project JonesForth from x86 assembly + forth to julia + forth, although the
-mapping is in a few places non-trivial due to the fact that julia is a high
-level language. A huge proportion (say 80%) of the library code in src/lib.4th
-is directly copied from JonesForth. I've added some additional core definitions
-and modified some of the others to be a little bit closer to the behaviour of
-ANS forth (or at least FORTH 83).
+A hobby implementation of a forth system atop the Julia scientific computing
+language. It will almost certainly never be useful for any purpose besides
+that which it has already fulfilled: forcing me to think quite carefully about
+how forth works.
+
+This package owes a massive debt to the existence of the literate programming
+project [JonesForth](https://rwmj.wordpress.com/2010/08/07/jonesforth-git-repository/),
+which was an amazing read. To a large degree my package is simply a port of
+that project from x86 assembly + forth to julia + forth, although the mapping
+is in a few places non-trivial due to the fact that julia is a high level
+language. During the bootstrapping process, a huge proportion (say 80%) of the
+library code in src/lib.4th was directly copied from JonesForth. (The fact
+that it was possible to reuse this code was satisfying in its own right!) Since
+that time I've added a significant number of core definitions and modified some
+of the others with the eventual aim of F83 compliance (discussed below).
There's quite a lot to say about the implementation, especially due to its
high-level grounding, but that will have to wait for another time.
julia> Pkg.clone("https://github.com/tgvaughan/forth.jl")
+Currently, forth.jl **requires** Julia 0.5. (Incompatabilities between 0.4 and 0.5
+mean that I cannot support both versions.)
+
## Usage
To start the interpreter/compiler running, simply enter the following at
The first thing the interpreter will do is compile the core definitions in
the library file. Once this is complete you can start entering forth commands:
- : star 42 emit ;
- ok
- star
- * ok
-
-Notice that unlike other forths, forth.jl echos a newline after reading each
-line of standard input. This is an unfortunate side-effect of the way that
-I've implemented the primitive word KEY. Hopefully I'll be able to fix this
-in future.
+ : star 42 emit ; ok
+ star * ok
There's an example Mandelbrot Set drawing program included in the examples
-directory. To run it, you'll have to locate this directory on your system
-(its location depends on what OS you happen to be using). Once found, use
-the "INCLUDE" word to compile its definitions. For example, on my system
-I can run the example in this way:
+directory. To run it, use the `INCLUDE-LIB` word to open the file and compile its
+definitions:
- include /home/tim/.julia/v0.4/forth/examples/mandelbrot.4th
+ include-lib ../examples/mandelbrot.4th
Enter 'mandel' to draw the Mandelbrot Set. ok
mandel
*
**
ok
+(`INCLUDE-LIB` is exactly like INCLUDE, but includes files relative to thte
+platform-dependent forth.jl src/ directory.) To exit, enter ^D on a blank line
+or use the `BYE` word.
+
+## FORTH-83 Compliance
+
+One of my goals has been to have forth.jl contain as much of the
+[F83 required word set](http://forth.sourceforge.net/standard/fst83/fst83-12.htm)
+as makes sense given the underlying VM. (Actually, my main goal goes a bit
+beyond this: I want to forth.jl to be, with a couple of exceptions, compatible
+with the description of forth contained in the second edition of Leo Brodie's
+book "Starting Forth".) I'm fairly happy with my progress so far. Of the
+131 required F83 words, only 20 remain unimplemented. These words fall into
+two categories: those I may possibly implement at some point, and those that I
+do not intend to ever implement for reasons of obsolescence or incompatibility
+with the design of the VM.
+
+### F83 Words that may be implemented someday
+
+ # #> #S -TRAILING <#
+
+These words all have to do with number to string conversion, something I've
+not been interested in enough yet to get on top of.
+
+### F83 Words that won't be implemented
+
+ D+ D< DNEGATE U< UM* UM/MOD BLOCK BUFFER FLUSH
+ SAVE-BUFFERS UPDATE BLK HOLD LOAD FORTH-83
+
+These words don't make sense to implement. The double-length integer words are
+useless because the smallest unit of memory in our VM is a full 64 bit
+integer. For the same reason, there's no point in dealing with unsigned values
+just to gain access to another bit. The block I/O words don't make sense because
+we have access to a filesystem via the OS.
+
## License
This package is free software and is distributed under version 3.0 of the GNU
The Lambda Lab / projects / forth.jl.git / blobdiff