Multiline functions in Commodore 64 BASIC

Question

So, I would like to write larger functions in Commodore 64 BASIC. So far, from what I see from other sources (such as the various C64 wikis, as well as the user guide for C64 itself), function definitions can only be one line long. That is, I cannot find a similar construction in BASIC for brackets / any other languages ​​used to highlight blocks of code.

Does anyone know how I will write blocks of code in BASIC that consist of several lines?

One line function example:

10 def fn X(n) = n + 1 20 print fn X(5) rem Correctly called function. This will output 6 

But I can not do something like:

 10 def fn X(n) = 20 n = n + 1 30 print n 40 rem I'd like the definition of function X to end at line 30 above 50 fn X(5) rem Produces syntax error on line 40 

Thank you for your time!

Answer 1

Sadly, the C64 BASIC does not support more complex features.

However, it does support more complex routines and what you want in this case.

 10 rem you can set up n in advance here 20 n = 23 30 gosub 50 40 rem n is now 24 50 rem start of subroutine; this line is not needed, it just here for clarity 60 n=n+1 70 print n 80 return 90 rem now you can call the subroutine on line 50 and it'll return at line 80 

Unfortunately, passing parameters to and returning values ​​from routines in C64 BASIC is not a formalized construct, so you just have to work with ordinary variables, as shown above.

Answer 2

From what I remember, you can do this almost with colan to have multiple commands on the same line. Not the most elegant solution, but will allow you to figure out:

 10 def fn X(n) = 20 n = n + 1 30 print n 40 rem I'd like the definition of function X to end at line 30 above 50 fn X(5) rem Produces syntax error on line 40 

becomes

 10 n=n+1: print n 

Note that you cannot pass arguments, so you have to declare things and let the BASIC stack take care of this for you. Usually I would structure such programs:

 1 rem lines 1-99 are definitions. 2 n% = 0 : rem this declares the variable n as an integer, initializing it to 0 100 rem lines 100-59999 are the core code 101 n%=5 : gosub 60100 59999 end : rem explicit end of the program to ensure we don't run into our subroutine block 60000 rem lines 60000+ are my subroutines.. 60100 n% = n% + 1 : print n% : return 

It has been a while; from memory, the% symbol is what declares the variable as an integer, like $ declaring it as a string.

Answer 3

You can use existing variables and mathematical commands with DEF FN , for example, if you want to PRINT from 0 to 10 inclusive in 4-bit nybbles, you could do this:

  0 DEF FN B(X)=SGN(X AND B) 1 FOR I=0 TO 10: REM OUR COUNTER 2 B=8: REM OUR BIT MARKER (128, 64, 32, 16, 8, 4, 2, 1) 3 FOR J=0 TO 3: REM WE WANT 4-BIT NYBBLES, SO 0 TO 3 INCLUSIVE 4 PRINT RIGHT$(STR$(FN B(I)),1);: REM CALLS OUR FUNCTION 5 B=B/2: REM MOVES TO NEXT BIT MARKER 6 NEXT J: REM PROCESS FOR LOOP J 7 PRINT: NEXT I: REM NEW LINE THEN PROCESS FOR LOOP I 

I tried nesting functions, but it gets too confusing. In fact, I have not seen many lists that use DEF FN . Maybe some senior hipster master BASIC programmers use them?