README.md

   1 # forth.jl
   2
   3 A hobby implementation of a forth system atop the Julia scientific computing
   4 language.  It will almost certainly never be useful for any purpose besides
   5 that which it has already fulfilled: forcing me to think quite carefully about
   6 how forth works.
   7
   8 This package owes a massive debt to the existence of the literate programming
   9 project [JonesForth](https://rwmj.wordpress.com/2010/08/07/jonesforth-git-repository/),
  10 which was an amazing read. To a large degree my package is simply a port of
  11 that project from x86 assembly + forth to julia + forth, although the mapping
  12 is in a few places non-trivial due to the fact that julia is a high level
  13 language.  During the bootstrapping process, a huge proportion (say 80%) of the
  14 library code in src/lib.4th was directly copied from JonesForth.  (The fact
  15 that it was possible to reuse this code was satisfying in its own right!) Since
  16 that time I've added a significant number of core definitions and modified some
  17 of the others with the eventual aim of F83 compliance (discussed below).
  18
  19 There's quite a lot to say about the implementation, especially due to its
  20 high-level grounding, but that will have to wait for another time.
  21
  22 ## Installation
  23
  24 forth.jl is not (and probably will never be) a registered julia package.  To
  25 install it, you will therefore need to use the following command from the
  26 Julia package manager (accessed using the `]` key):
  27
  28     (v1.0) pkg> add https://github.com/tgvaughan/forth.jl
  29
  30 Be aware that **forth.jl requires Julia 1.0**. (Incompatabilities exist between
  31 0.6 and previous versions of julia, particularly the handling of [world age](https://github.com/JuliaLang/julia/pull/17057).)
  32
  33 ## Usage
  34
  35 To start the interpreter/compiler running, simply enter the following at
  36 the julia prompt:
  37
  38     julia> import forth
  39     julia> forth.run()
  40
  41 The first thing the interpreter will do is compile the core definitions in
  42 the library file.  Once this is complete you can start entering forth commands:
  43
  44     : star 42 emit ;  ok
  45     star * ok
  46
  47 There's an example Mandelbrot Set drawing program included in the examples
  48 directory.  To run it, use the `INCLUDE-LIB` word to open the file and compile its
  49 definitions:
  50
  51     include-lib ../examples/mandelbrot.4th
  52     Enter 'mandel' to draw the Mandelbrot Set. ok
  53     mandel
  54                                                                                 *
  55
  56                                                                            **
  57                                                                         ********
  58                                                                        *********
  59                                                                          *****
  60                                                           ***     ********************
  61                                                            ****************************** ****
  62                                                           **********************************
  63                                                        ***************************************
  64                                                      ********************************************
  65                                   **    *            *******************************************
  66                                   *************    *********************************************
  67                                ******************  ********************************************
  68                                ******************* ********************************************
  69          **    *     *  *******************************************************************
  70                                ******************* *******************************************
  71                                 *****************  ********************************************
  72                                   *************     ********************************************
  73                                   **    *           ********************************************
  74                                                      ********************************************
  75                                                         **************************************
  76                                                          ***********************************
  77                                                            ****************************** ****
  78                                                            **     ********************
  79                                                                          *****
  80                                                                         *******
  81                                                                        *********
  82                                                                            **
  83     ok
  84
  85 (`INCLUDE-LIB` is exactly like INCLUDE, but includes files relative to thte
  86 platform-dependent forth.jl src/ directory.) To exit, enter ^D on a blank line
  87 or use the `BYE` word.
  88
  89 ## FORTH-83 Compliance
  90
  91 One of my goals has been to have forth.jl contain as much of the
  92 [F83 required word set](http://forth.sourceforge.net/standard/fst83/fst83-12.htm)
  93 as makes sense given the underlying VM. (Actually, my main goal goes a bit
  94 beyond this: I want to forth.jl to be, with a couple of exceptions, compatible
  95 with the description of forth contained in the second edition of Leo Brodie's
  96 book "Starting Forth".)  I'm fairly happy with my progress so far.  Of the
  97 131 required F83 words, only 20 remain unimplemented.  These words fall into
  98 two categories: those I may possibly implement at some point, and those that I
  99 do not intend to ever implement for reasons of obsolescence or incompatibility
 100 with the design of the VM.
 101
 102 ### F83 Words that may be implemented someday
 103
 104     # #> #S -TRAILING <#
 105
 106 These words all have to do with number to string conversion, something I've
 107 not been interested in enough yet to get on top of.
 108
 109 ### F83 Words that won't be implemented
 110
 111     D+ D< DNEGATE U< UM* UM/MOD BLOCK BUFFER FLUSH
 112     SAVE-BUFFERS UPDATE BLK HOLD LOAD FORTH-83
 113
 114 These words don't make sense to implement.  The double-length integer words are
 115 useless because the smallest unit of memory in our VM is a full 64 bit
 116 integer.  For the same reason, there's no point in dealing with unsigned values
 117 just to gain access to another bit.  The block I/O words don't make sense because
 118 we have access to a filesystem via the OS.
 119
 120 ## License
 121
 122 This package is free software and is distributed under version 3.0 of the GNU
 123 General Public License, which may be found in the file LICENSE in this
 124 directory.