World: r3wp

The start of a BBC BASIC interpreter using string parsing: http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.r

How do we best get this rolling? I'm interested in making some language 
interpreters in REBOL, because I see future potential. Reichart and 
Gregg talked about QBASIC, which I don't know. Where are the specifications 
for that language? BASIC is a start, and along the line, I would 
like to dig into other languages as well. Is it best keeping it all 
public, or should we make new groups for teams interested in this?

Very nice...  As for the other questions...can't say...but well done 
sir.  And a nice reading code space to boot.

Nice John! I'm not sure how best to get rolling. I'm totally buried 
at the moment, but I can provide web space for the project if we 
need that. I also a number of grammars and things here, if we need 
references.

Oddly, I don't seem to have a QBASIC grammar. :-\

I started on a VB grammar once, which is similar, and I still have 
most of my manuals here somewhere. :-)

Not sure if the various sites for lex/yacc tools and such might have 
one/

Gregg, first I'm making a simple 'engine' or 'template' for BASIC. 
Today I implemented expressions, some simple string handling and 
a little more. I'll make conditions (IF) and loops (FOR), then that 
should be a good start to build on.

Uploaded new version of BBC BASIC intepreter. Added expressions and 
conditions. Added IF and INPUT. Example:

>> do http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.r
connecting to: www.fys.ku.dk
Script: "BBC BASIC" (18-Jul-2007)
BASIC v. 0.0.2 

>auto
   10 input "Name",name$

   20 if name$="Carl" then print "Hi " name$ else print "Hello " name$
   30 0
>run
Name?John
Hello John

So far this is implemented:

Keywords: AUTO, DELETE, LIST, NEW, OLD, GOTO, RUN, END, IF, INPUT, 
LET, PRINT, REM, STOP
Functions: COS, SIN
Expressions can beside unary +, - use: +, -, *, /, ^, (, )
Conditions can use: or, eor, and, =, <>, <=, >=, <, >

It's possible to add strings together and strings can also be tested 
in conditions.

3 datatypes is implemented. Examples:
a$ is a string
a% is an integer
a is a real.

*are implemented*

Use a zero (0) to leave AUTO. Pressing <Esc> will end the BASIC intepreter.

New version 0.1.0 of BBC BASIC. Added FOR ... NEXT loop. Example:

>> do http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.r
connecting to: www.fys.ku.dk
Script: "BBC BASIC" (19-Jul-2007)
BASIC v. 0.1.0 

>auto
   10 for a=10 to pi step -2.3
   20 for n%=1 to 3 step 2
   30 print a n%
   40 next
   50 next
   60 0
>run
                  10                   1
                  10                   3
                 7.7                   1
                 7.7                   3
                 5.4                   1
                 5.4                   3

Cute.

A modern BASIC should maybe be able to recognize both lower an UPPER 
case, like in my examples. The original BBC BASIC distinguish between 
upper and lower case. I should change my interpreter to work this 
way, so already written programs will work.

Or maybe the problem is only with variables!? Hmm

http://www.programatium.com/en/programming4/qbasic.htm
http://www.qbasic.com/wbb/filebase_entry.php?entryid=50&

New version 0.1.1 of BBC BASIC. Added many keywords, mostly functions. 
To run:
>> do http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.r

List of keywords: http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.html

Version 0.2.0 of BBC BASIC uploaded. Added DATA, READ and RESTORE. 
Added GOSUB and RETURN. Added hex notation, made some changes and 
fixed bugs.

This is meant as an implementation of BBC BASIC originally found 
on the BBC Micro from british Acorn. It's not an emulator of that 
computer. For emulation of the BBC Micro, I recommend BeebEm.

One thing is to implement old languages, it could also be interesting 
to make a modern BASIC using block parsing in REBOL. That way, it 
would be possible to easily implement many of the datatypes found 
in REBOL. Also imagine to be able to have BASIC (or other language) 
code in the middle of a REBOL script, doing something like:
... (some REBOL code) ...
BASIC [
... (some BASIC code) ...
]
... (more REBOL code) ...

The BBC BASIC interpreter is now more than 800 lines of REBOL source 
(or 20278 bytes). It's 4568 bytes compressed.

In the early 80'ies, before the era of PCs, the Amiga, Mac and Linux, 
there were a whole range of home computers more or less expensive 
(the BBC Micro were in the high price range back then). They all 
came with some version of the BASIC language. It was also possible 
to program in assembler (the BBC had a 6502 CPU). Imagine a new homecomputer 
with REBOL and rebcode. And many other languages supported as REBOL 
dialects. It should just have a keyboard, network, some RAM and maybe 
a memory stick instead of a harddisk. And connection to a monitor. 
That shouldn't be too costly to produce. Would it sell if the price 
was right?

Oh, and it should have a low-energy CPU to run the scripts, something 
as the G3, I think IBM made to only use 1-2 Watt. Then it could be 
sold all over the World.

geomol, I think you'd have to price it like a midsized calculator

I think also we need a new age of exploratory computing (meaning, 
people exploring other than porn sites and youtube), and it requires 
its own hardware.

the problem is that people expect to do everything on a PC, whereas 
in the 80's, people expected to do everything on a C64.

Geomol - there is one strong and modern Basic implementation - Free 
Basic?

Pekr, is it strong enough? As datatypes, it support different kinds 
of integers, floating-point and strings. BASIC as a REBOL dialect 
would be able to have much more, wouldn't it?

Wow John! I haven't even had a chance to look at it since the original 
release and you're already on v2, well, 0.2, but still. :-) And, 
yes, I think it would be very cool to have a BASIC that supports 
REBOL's datatypes. Part of my, perhaps not so hidden, agenda for 
these things--in addition to being great for teaching language design 
and construction--is to show how REBOL can work *inside* the idioms 
other languages use.

:-) I have a feeling, that dialects is a good way to go, because 
so many problems become much easier to solve.

Geomol, the problem with such a computer is that it would only appeal 
to geeks, and geeks already have a pc anyway. for developing countries, 
there's the OLPC eventually.

i think, time would better be invested in an OS (both for geeks, 
and non-geeks). then you can make cheap computers for the OS to run, 
once it has been recognized, so parents could buy a $100 computer 
to childs (one each) instead of one big $1000 pc for the family.

(http://news.yahoo.com/s/nm/20070720/od_nm/nigeria_pornography_dc;_ylt=A0WTUfF176FG8XwBExgZ.3QA)

Somthing that translates to all  languages, and ages...

Version 0.3.0 of BBC BASIC uploaded. Added the rest of the string 
handling: LEFT$, MID$, RIGHT$, STRING$ and INSTR. Added ON, that 
can change the order of execution. Added DIM, which implement arrays. 
Both for integers, reals and strings. To run:
>> do http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.r

List of keywords: http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.html

Arrays are indexed from zero. Arrays can also be used to index other 
arrays. Example:

>dim name$(4)
>dim a(1,1)
>name$(3)="Joe"
>a(1,0)=3
>print name$(a(1,0))
Joe

BBC BASIC v. 0.4.0 uploaded. Added procedures and local variables 
(DEF PROC, ENDPROC and LOCAL). Added TIME, RND and EVAL. Added better 
error handling. Next thing will be functions, but I'll test procedures 
some more first. The implementation is based on this user guide: 
http://www.nvg.ntnu.no/bbc/doc/BBCUserGuide-1.00.pdf

It's now almost 1400 lines of REBOL source. But still only 4922 bytes 
compressed.

Example use of local variables. In line 70, 'a' is local, because 
it's a parameter to the procedure, 'b' is still global. After line 
80, 'b' also become local to the procedure. After returning from 
the procedure, both 'a' and 'b' are set back to their global values. 
In 'proctest', 'a' could have been called anything without changing 
the global 'a'.

>> do http://www.fys.ku.dk/~niclasen/rebol/bbcbasic.html
Script: "BBC BASIC" (27-Jul-2007)
BASIC v. 0.4.0 

>auto
   10 a=42
   20 b=1
   30 proctest(a)
   40 print "line 40 : a=";a " b=";b
   50 end
   60 def proctest(a)
   70 print "line 70 : a=";a " b=";b
   80 local b
   90 a=2:b=2
  100 print "line 100: a=";a " b=";b
  110 endproc
  120 0
>50end
>run
line 70 : a=        42 b=         1
line 100: a=         2 b=         2
line 40 : a=        42 b=         1

Ups, the line
>50end

after the program shouldn't have been there, so forget that (even 
if it works with it included).

There still need to be work done on formatted output (PRINT and INPUT 
statements).

So far, I've allowed keywords to be either UPPER- or lower-case. 
I think, I have to restrict them to UPPER-case like in traditional 
BASIC. Problem is with variable names being assigned by the LET statement. 
If I define a variable "length":
LET length=10

and then use it in some expression, the first part of the variable 
name is being recognized as the LEN function. In the original BBC 
BASIC, the above LET statement is ok, while you can't write:
LET LENGTH=10

, which will give a syntax error. I conclude, I have to restrict 
keywords to UPPER-case and then check, when the variables are being 
defined, so their names don't collide with keywords.

This probably the same reason, words are separated by space in REBOL.

This *is* ...

It's rather difficult to implement functions (user functions, which 
the BBC BASIC language support), with the implementing method, I've 
choosed. Problem is, that the return point need to be saved, while 
the function code is running. The problem is the same with statements 
like GOSUB and PROC (procedures), but so far, I've just put some 
restrictions on those. In this basic, more than one statement can 
be on each line, if they're separated by colons, ':'. The way it's 
implemented, this example give a syntax error:
GOSUB 100:PRINT "I'm back"

My implementation require, that the return point is the next line. 
That isn't good enough with functions, because they're used in the 
middle of other statements. Examples:

PRINT FNone_function, FNanother_function
IF FNmyfunc=42 THEN PRINT "It's 42!"


The return point for those need to be in the middle of a statement, 
in the middle of a line. So I'm at a point, where I consider another 
implementation of all the statements (more like a real emulation 
of the BBC computer) or if I just should say "the heck with it" and 
move on to some other language or another version of a new BASIC 
language.

Comments!?

Comments, hmmm.  You've done an awesome job John.  I learned Z-80 
assembler back on my TRS-80 before I did much BASIC.  When they finally 
got a computer class in my high school for ninth graders, I was already 
in grade 12 and laughed at the BASIC.  So, instead of having me whining 
and whinging all class, I got to write a student database program 
in assembler for my electronics teacher on the Commodore PET.  Never 
been a fan of BASIC, but what you've done can only attract a larger 
REBOL audience so well done.  If you can make it compatible enough 
to run old DOS frogger.bas you may have a demo that gains worldwide 
attention.


Technically, back to your point, (having sadly only glossed over 
your codebase), what if you tricked the "line" internals say with 
pair! or decimal! keeping your own sub-lines invisible to the user?


And if you start up a Forth dialect...I'm in.   Or at least will 
show a keener interest watching a guru at work   :)