QB64-interpreter

[FellippeHeitor]

This started when Joe Jankovic (I can't for the life of me remember what his user name in the .net forum is) asked for help with a parsing routine he was writing for the CIRCLE command.

I started building this interpreter around his CIRCLE routine, with my added fixes.

After that it was just a matter of "hey, I think I can make it do this" and "it'd be easy to do that" and so it keeps on growing till today.

The source code so far:
https://raw.githubusercontent.com/FellippeHeitor/QB64-interpreter/master/basiccmdline.bas

Command Reference:
Files
NEW
LOAD <file>
RELOAD
SAVE [file]

Interpreter/editing
RUN
LIST [line number]
LIST PAUSE
LIST VARIABLES
EDIT <line number>
INSERT <line number>
DELETE <line number/interval>

Functions supported:
INT
ASC
COS
SIN
LEN
RND
TIMER
TIME$
DATE$
INKEY$
_WIDTH
_HEIGHT
_MOUSEX
_MOUSEY
_MOUSEBUTTON
(no need to query _MOUSEINPUT for mouse functions)

Disk
CHDIR <path>
MKDIR <path>
FILES [filespec$]
KILL <file>

Text and Graphics output
PRINT (limited support)
SCREEN (legacy modes only)
_DISPLAY
WIDTH
COLOR
LOCATE
CIRCLE
CLS

Others
RANDOMIZE
_LIMIT
KEY ON/OFF
SLEEP
_TITLE
SYSTEM
END
INPUT

Special blocks
DO (no WHILE or UNTIL yet)
    EXIT DO
LOOP

IF <condition> THEN (no single line IFs yet)
    'code
END IF

CTRL+C can be used to break out of a running program.
Commands are run immediately after they are typed. If you load a file from disk with the LOAD command you can see the listing with LIST and then RUN it. All of the following samples have been created to test the current state of the interpreter and work as expected:

Code: QB64: [Select]

1. cls
2. PRINT "Counting to 10:"
3. a = 0
4. DO
5.     a = a + 1
6.     COLOR a
7.     PRINT a
8.     IF a = 10 THEN
9.         EXIT DO
10.     END IF
11. LOOP
12. COLOR 15
13. PRINT "Done."
14. COLOR 7

Code: QB64: [Select]

1. CLS
2. COLOR 3, 1
3. PRINT "Hello! ";
4. COLOR 15, 6
5. PRINT "It's me!"
6. COLOR 7, 0
7. PRINT "What's your name? ";
8. INPUT name$
9. PRINT "Enter a color for the text: ";
10. INPUT fg
11. PRINT "Enter a color for the bg: ";
12. INPUT bg
13. COLOR fg, bg
14. PRINT
15. PRINT "Listen, ";
16. PRINT name$;
17. PRINT "..."
18. PRINT "I'll sleep for 2 seconds..."
19. SLEEP 2
20. COLOR 7, 0
21. END

Code: QB64: [Select]

1. SCREEN 13
2. DO
3.     x = RND * _WIDTH
4.     y = RND * _HEIGHT
5.     r = RND * 20
6.     c% = RND * 255
7.  
8.     CIRCLE (x, y), r, c%
9.  
10.     _DISPLAY
11. LOOP

Code: QB64: [Select]

1. SCREEN 13
2. KEY OFF
3. PRINT "Click around..."
4. DO
5.     IF _MOUSEBUTTON(1) = -1 THEN
6.         r = RND * 50
7.         c% = RND * 255
8.         CIRCLE (_MOUSEX, _MOUSEY), r, c%
9.     END IF
10.  
11.     _LIMIT 60
12.     _DISPLAY
13. LOOP
14. KEY ON

Code: QB64: [Select]

1. CLS
2. PRINT "Seconds to count:";
3. INPUT sec
4. IF sec = 0 THEN
5.     PRINT "Bummer..."
6.     END
7. END IF
8.  
9. IF sec > 10 THEN
10.     sec = 10
11.     PRINT "That's just too long."
12. END IF
13.  
14. PRINT "Will wait for";
15. PRINT sec;
16. PRINT "seconds..."
17.  
18. s = TIMER
19. DO
20.     t = TIMER - s
21.     IF t > sec THEN
22.         EXIT DO
23.     END IF
24. LOOP
25.  
26. PRINT "done!"

Code: QB64: [Select]

1. KEY OFF
2. DO
3.     CLS
4.     a = RND * 14
5.     a = a + 1
6.     COLOR a
7.     LOCATE 1, 1
8.     PRINT TIME$
9.     _DISPLAY
10.     _LIMIT 30
11.     a$ = INKEY$
12.     b = LEN(a$)
13.     IF b > 0 THEN
14.         PRINT "A key was pressed."
15.         COLOR 7, 0
16.         KEY ON
17.         EXIT DO
18.     END IF
19. LOOP

[Ashish]

AWESOME!!!!!!

[bplus]

Hey Fellippe!

You do the do loop like I do! Only way out is through an Exit command, right?

ELSE for IF THEN block done very much like looking for LOOP at same level as EXIT.

Oh wait, can yours do nested loops? It doesn't look like you are checking levels.

Have you tested code with an internal loop after EXIT DO command in outer loop?

Do
    ...
    if ...
        exit do
    end if

    do
    ...
    loop
    ...
Loop

[FellippeHeitor]

Hi bplus,

No nested structures in this iteration.

This is still very much in infancy; I'll eventually get to that.

Fellippe

[bplus]

Hi Fellippe,

So yours can list variables? Nice idea, if I am correct (I am only skimming through code).

And macros for save, ... nice! (again if I read right)

[FellippeHeitor]

LISTing variables and code only works in immediate mode, as well as source code file features like SAVE, LOAD, NEW.

[FellippeHeitor]

I must also add that math features are very limited.

[bplus]

Hi Fellippe,

Well I love your start!

[STxAxTIC]

Lovely, just lovely. This will be a great toy to play with. While it's still early, I'd like to hear your arguments for or against the idea of separating mechanism from interface, such that the (for lack of a better term) "logic unit" can be decoupled from screen drawing, for example. This way, you can install the brain into different places - chatbots, a scripting option within inform, etc.

[bplus]

Hi,

I just tested a drag and drop of a bas file onto the exe, it works! :)

[FellippeHeitor]

Good to hear!

If you write any sample code that runs well with it, please share it here.