Gforth
GNU Forth is a fast and portable implementation of the ANSI Forth language.
Forth is a low-level language being composed of a stack based virtual machine that is only slightly more abstract than hand written assembly language. It is a common task assigned to computer science undergraduates to write a Forth implementation from scratch in assembler. This is often done on microcontrollers with too few registers to easily support C, such as the MOS 6502.
Because it is designed to be portable, GNU's implementation of Forth, gforth, is written in portable ANSI C.
Installation
USE flags
USE flags for dev-lang/gforth GNU Forth is a fast and portable implementation of the ANSI Forth language
Emerge
root #emerge --ask dev-lang/gforthEnvironment variables
- GFORTHHIST – specifies the location of .gforth-history. Default: $HOME.
- GFORTHPATH – specifies the location of Forth source files.
- LANG – see LC_CTYPE
- LC_ALL – see LC_CTYPE
- LC_CTYPE – By default this is set to UTF-8, otherwise an 8-bit encoding is used. If LC_CTYPE is unset, Gforth checks LC_ALL and LANG (in that order) for character encoding information.
Files
- ~/.gforth-history — Per user configuration file (default).
Invocation
user $cmd --helpgforth --help Usage: gforth [engine options] ['--'] [image arguments] Engine Options: --appl-image FILE Equivalent to '--image-file=FILE --' --clear-dictionary Initialize the dictionary with 0 bytes -d SIZE, --data-stack-size=SIZE Specify data stack size --debug Print debugging information during startup --diag Print diagnostic information during startup --die-on-signal Exit instead of THROWing some signals --dynamic Use dynamic native code -f SIZE, --fp-stack-size=SIZE Specify floating point stack size -h, --help Print this message and exit --ignore-async-signals Ignore instead of THROWing async. signals -i FILE, --image-file=FILE Use image FILE instead of `gforth.fi' -l SIZE, --locals-stack-size=SIZE Specify locals stack size -m SIZE, --dictionary-size=SIZE Specify Forth dictionary size --no-dynamic Use only statically compiled primitives --no-offset-im Load image at normal position --no-super No dynamically formed superinstructions --offset-image Load image at a different position -p PATH, --path=PATH Search path for finding image and sources --print-metrics Print some code generation metrics on exit --print-sequences Print primitive sequences for optimization -r SIZE, --return-stack-size=SIZE Specify return stack size --ss-greedy Greedy, not optimal superinst selection --ss-min-codesize Select superinsts for smallest native code --ss-min-ls Minimize loads and stores --ss-min-lsu Minimize loads, stores, and pointer updates --ss-min-nexts Minimize the number of static superinsts --ss-number=N Use N static superinsts (default max) --ss-states=N N states for stack caching (default max) --tpa-noequiv Automaton without state equivalence --tpa-noautomaton Dynamic programming only --tpa-trace Report new states etc. -v, --version Print engine version and exit --vm-commit Use OS default for memory overcommit SIZE arguments consist of an integer followed by a unit. The unit can be `b' (byte), `e' (element; default), `k' (KB), `M' (MB), `G' (GB) or `T' (TB). Image Options: FILE load FILE (with `require') -e STRING, --evaluate STRING interpret STRING (with `EVALUATE') Report bugs on <https://savannah.gnu.org/bugs/?func=addbug&group=gforth>
Troubleshooting
Gforth isn't recognizing my shabang line
Gforth has a slightly weird shabang syntax compared to other interpreters.
The Gforth interpreter treats the shabang as a special type of comment and accepts the executable path that follows as an argument. To pull this off, it requires a space between #! and the path to the Gforth executable. Consequently, the shabang line has to look something like this:
example.fsA proper Gforth shabang line#! /usr/bin/env gforth
\ Your Forth code here.
Defining new words uexpectedly results in an undefined word Error
This is a very common mistake for those new to Forth. A space must exist between the : and the start of the word definition. Similarly, after the word definition ends there must be a space prior to the ; which ends the word. Thus, a valid word definition might look like this:
: foo <the logic of foo> ;
The is a consequence of the fact that the space character delineates tokens in Forth.
Removal
Unmerge
root #emerge --ask --depclean --verbose dev-lang/gforthExternal resources
- Learn Forth in Y Minutes.
- DurexForth a modern Forth in active development targeting the Commodore 64.