I sat around trying to think of a witty, pithy way to make this
announcement more surreal or frightening than it really is and failed. So
I guess I'll let it stand on it's own.
I've just completed a complete re-write of BASIC for Parrot. This time
I've used QuickBASIC as a model which means there's all kinds of new
features, and it's a much friendlier language to work with. It's not
complete, but a few tutorials that I found for QuickBASIC can be completed
with this compiler.
If you're interested, you can get the bundle
at http://geeksalad.org/basic/basic2.zip and eventually I suppose I'll
hack it into the languages\basic CVS tree in the Parrot distribution. The
compiler itself is rather hideous Perl, but the output and the runtime
libraries are all pure PASM.
Of interest specifically to p6i:
This version *almost* works flawlessly under 0.0.8 from about two weeks
ago. There's still some memory issues and large programs (like
newtrek.bas) that run long enough will segfault. So right now the
RT_initialize.pasm file has "collectoff" and "sweepoff" statements and that
seems to avoid the symptom.
Enjoy. :)
From the README file:
----------------------------------
Parrot BASIC 2.0
What is it?
It's an implementation of BASIC in Parrot. Unlike version 1, this is modeled
after Microsoft's QuickBASIC version 4.5. A quick list of features:
* It's compiled directly to Parrot Assembly (PASM) and not
interpreted.
* Richer syntax than Parrot BASIC 1.0, which was modeled after
GW-BASIC
* Much, much faster than Parrot BASIC 1.0
* Support for user-defined types
* Support for variable scopes+
(+ QB has bizarre ideas of scope. Caveat Programmer.)
I couldn't find a proper book on QuickBASIC, and believe it or not Google
wasn't
terribly helpful in finding a good manual. I did have a QB.exe and a few
help files for information.
What's missing?
The things that are missing fall into three classes.
"Someday I'll do these, there's hooks for it but I need a break now."
* Keywords: defint const static ubound
* SHARED in DIM statements
* Exception handling
* The keyword USING
* The "* length" modifier for strings
* Forward-declarations (DECLARE) are missing. For now, your DIM's and
functions must by defined before they're used.
* DEF FN. It's a special case of FUNCTION.
"These are *hard* and I may not do them, ever"
* Keywords: common chain bload bsave cseg
"These are nearly impossible given where Parrot is now.
maybe when the I/O gets rounded out and some libraries
get added. Like graphics, sound, and filesystem access."
* Keywords: screen pset preset line circle draw
view window pmap color palette paint
get put pcopy beep sound locate view
width resume pos poke peek rset
* Most directory manipulations
* Record (binary) I/O
And I probably have a whacked idea of I/O in QuickBASIC anyway.
What's incomplete?
Mostly the File I/O stuff. Surprisingly, basic file I/O is working properly.
See test #47.
What's a hack?
Dirty little secrets of PB2; some good, some bad:
* single/double are simply Parrot Nx registers
* int/long are simply Parrot Ix registers
* Everything is case insensitive.
* Arrays are really hashes. Yes, "foo(a$)" is now legal BASIC. I'll
sneak a "keys()" function into BASIC eventually...
* Other bad syntax is forgiven or Something Interesting happens
* The _STARTASM directive lets you put PASM in your BASIC code.
(see testsuite.pl for an example)
* I couldn't wrap my brain around BASIC's scoping to write the
expression evaluator properly. It's a kind of dynamic scoping
that hurts my head. So the expression evaluator is a postfix
machine.
* The DIM statement doesn't really need to indicate any kind of
size at all. DIM a$(1) will set aside a$ as any n-dimension
array of any size.
* The random number generator is *intentionally* seeded with a
constant to make testing easier. Use "randomize timer" to mix
things up.
How do I get going? Quickstart?
1. Edit "testrun.pl" and change the pathname at the beginning of the
script to wherever parrot is.
2. Type "compile.pl wumpus2.bas"
This produces "TARG_test.pasm" and "TARG_localfuncs.pasm"
3. Type "testrun.pl" and enjoy.
eliza2 and wumpus2 are simply ports from the Parrot BASIC 1.0 version. All
that had to be done were to add DIM statements and a RANDOMIZE. See the notes
below for more examples.
Where's the advanced syntax stuff?
Once you've fixed "testrun.pl" as noted above, the script "testsuite.pl" will
run BASIC through its self-tests. If you look through the script there's
examples
of almost every kind of syntax that I've got working.
What are all of these files?
RT_* Runtime Libraries. Things like the expression evaluator
and builtin functions (add, sub, mul, sin, cos, etc..)
COMP_* The compiler itself. Please, oh please don't look at this
Perl code. It's terrible. The intention is to re-write the
code in PASM and so it's very wide-open and loose for easier
translation.
TARG_* The output from the compiler. TARG_test.pasm is the main body
of your program. TARG_localfuncs.pasm is any functions and
subroutines you've declared.
compile.pl
The Compiler. Call as "compile.pl filename.bas" to compile
a BASIC program.
testrun.pl
Calls the assembler to put the program together and runs it.
testsuite.pl
The regression test, to make sure I haven't botched anything.
eliza2.bas
wumpus2.bas
GW-BASIC programs "ported".
newtrek.bas
Super Star Trek, demo for PB2 syntax
readme.bas
Reads through this readme file
END
