language and parsing
A number of years ago I had an idea for an extended "sed" (stream editor) language, that would parse and translate ("compile") complex free languages. I implemented it at bumble.sourceforge.net/books/pars/ . I wrote it in plain c. It is a strange beast, that seems useful and enjoyable to use. It allows one to think about language, parsing and compiling in a natural stream-oriented way. Its a simple virtual machine, an "assembly" language format, and a script language. It reads, parses and compiles itself and is almost as simple as "sed". The syntax is very similar to sed but the semantics are a bit different (the script cycle is character-by-character instead of line-by-line, for example).
The pep interpreter seems to work well and it has a useful debugger/ script viewer. Also, pep scripts can be translated into other languages. So I decided to write to people who seem to know about these things, hoping that someone would see this unpolished gem for what it is.
an example of a basic pep script is
read; get; put; clear; (eof) { get; print; }
This reverses the input stream.
I have written a few pep scripts that seem show off the potential of this mini-language. Here are some basic examples
http://bumble.sourceforge.net/books/pars/eg/palindrome.pss
scans the input for palindromes and reports the results.
http://bumble.sourceforge.net/books/pars/eg/exp.tolisp.pss
This converts (very) simple arithmetic expressions into a lisp-like
syntax with operator precedence.
http://bumble.sourceforge.net/books/pars/eg/json.check.pss
http://bumble.sourceforge.net/books/pars/compile.pss
This is a script (written in the parse-script language)
which implements the parse-script language. Well... at
the very beginning I had to "bootstrap" the language using
a program written in the "assembly" format. This is
http://bumble.sourceforge.net/books/pars/asm.pp But any
additions to the language syntax are now made to the
"compile.pss" script which compiles itself into a new
"asm.pp". So in a bash shell I do
pep -f compile.pss compile.pss > asm.new.pp; cp asm.new.pp asm.pp ,,,
http://bumble.sourceforge.net/books/pars/tr/translate.go.pss
This is a script which compiles pep scripts into standalone "go" source code. Similar translators exist for java, ruby, python, and c.
http://bumble.sourceforge.net/books/gh/eg/plzero.pss
This script parses and pretty prints PL/0 (a toy pascal like
language) source code
If you think this idea is interesting, it would be great if you could spare the time to review it and/or let other people know about it. The project is open-source. Thanks for reading!
regards
Matthew Bishop Sept 2021