6502.org

Code: Select all

10 for i = 1 to 10
20 if rnd(0) > 0.5 then 110
30 goto 80
40 rem here's a stray NEXT that doesn't belong to any loop
50 next
60 print "finished the wrong next!"
70 goto 130
80 next
90 print "first next finished"
100 goto 130
110 next
120 print "second next finished"
130 rem rest of the program

Code: Select all

> list
   10 input q
   20 if q > 10
   30   print q
   40   if q > 20
   50     print "big"
   60     endif
   70   print "small"
   80   endif
   90 print "done"
  100 end
> run
? 3
endif at line 60
small
done
> run
? 15
15 
endif at line 60
small
done
> run
? 25
25 
big
small
done
>

Code: Select all

> list
   10 input q
   20 if q > 10
   30   print q
   40   if q > 20
   50     print "big"
   60     endif
   70   endif
   80 print "small"
  100 end
> run
? 5
endif at line 70
small
> run
? 15
15 
endif at line 60
small
> run
? 25
25 
big
small
> 

Code: Select all

			do
			{
				printf ("for loop: line %d\n", *(uint16_t *)where);
				where = execute(where);
				printf ("where = %p\n", where);
			}
			while (NULL != where);

Code: Select all

> 10 for p = 1 to 3
> 20 print "hello "; p
> 30 next
> run
hello 1 
hello 2 
hello 3 
> 10 for p = 3 to 3
> run
hello 3 
> 10 for p = 4 to 3
> run
> 

Code: Select all

> list
   10 a = 0
   30 do
   35   b = 0
   40   do
   50     print a * 10 + b;
   60     b = b + 1
   70     while b < 10
   75   print
   80   a = a + 1
   90   while a < 10
  100 print "done"
> run
0 1 2 3 4 5 6 7 8 9 
10 11 12 13 14 15 16 17 18 19 
20 21 22 23 24 25 26 27 28 29 
30 31 32 33 34 35 36 37 38 39 
40 41 42 43 44 45 46 47 48 49 
50 51 52 53 54 55 56 57 58 59 
60 61 62 63 64 65 66 67 68 69 
70 71 72 73 74 75 76 77 78 79 
80 81 82 83 84 85 86 87 88 89 
90 91 92 93 94 95 96 97 98 99 
done
> 

Code: Select all

char * do_do (char * where)
{
	/* Execute the 'do' clause by calling it recursively; it continues
	 * until the matching 'while' statement. That statement returns NULL
	 * if its comparison clause is true, indicating that the loop should
	 * continue, or the address of the line following 'while'
	 */
	
	char * loop_address;	// first line in the do loop
	char * cont_address;	// first line after the while
	char * while_address;	// the while line number
	
	where -= 4;
	//printf ("do at line %d\n", get_line(where));
	where = find_next_line (where);
	loop_address = where;
	while_address = find_pair (where, DO);
	cont_address = find_next_line (while_address);	// first line after while
	//printf ("cont = %d, loop = %d\n", 
	//	get_line(cont_address), get_line(loop_address));
	do
	{
		where = loop_address;
		do
		{
			// when we execute the while, we are returned a NULL if the
			// condition is true
			//printf("do: executing line %d\n", get_line(where));
			where = execute(where);
			if (NULL != where)
			{
				//printf("in do: next line %d\n", get_line(where));
				if (get_line(where) == get_line(cont_address))
				{
					//printf ("break\n");
					break;
				}
			}
			else
			{
				//printf ("inner done, pointing to %d\n", get_line(where));
			}
		}	
		while (NULL != where);
	}
	while (NULL == where);
	//while (get_line(where) < get_line(while_address));
	return where;
}

uint8_t * do_while (uint8_t * where)
{
	/* test a condition; if true, return the value zero 
	 * otherwise, return the address of the next line
	 */
	 if (compare())
	 {
		 //printf ("while is true\n");
		 return NULL;
	 }
	 else
	 {
		 //printf ("while is false\n");
		 return find_next_line (where - 4);
	 }
	return where;
}