clean up part2, add documented version

day1/part2.bas

@@ -7,19 +7,18 @@ REM Written in Applesoft BASIC
  40  PRINT  CHR$ (4),"READ INPUT"
  100 S$ = ""
  110  GET C$
+ 115  GET D$
  120  IF  ASC (C$) = 13 GOTO 200
  130 S$ = S$ + C$
- 135  GET D$
  140  GOTO 110
  200 V =  VAL (S$)
- 205  GET D$
  210  IF V = 0 GOTO 300
  220 CURR = CURR + V
  230  GOTO 100
  300  FOR I = 0 TO 5
  310  IF CURR = CALS(I) GOTO 360
  320  IF CURR < CALS(I) THEN  NEXT I
- 330  FOR J = 3 TO I STEP  - 1:CALS(J + 1) = CALS(J): NEXT 
+ 330  FOR J = 3 TO I STEP  - 1:CALS(J + 1) = CALS(J): NEXT J
  340 CALS(I) = CURR
  350  PRINT CALS(0),CALS(1),CALS(2)
  360 CURR = 0

day1/part2_documented.bas

@@ -0,0 +1,67 @@
+REM Advent of Code 2022: Day 1, part 2
+REM Written in Applesoft BASIC
+
+REM ONERR will GOTO 900 on any error. For this program, the only error should be
+REM reaching the end of the input file.
+
+ 10  ONERR  GOTO 900
+
+REM Initialize the highest calories array and current calorie count.
+
+ 20  DIM CALS(5):CURR = 0
+
+REM Open the input file for reading. Printing CHR$(4) causes the following text
+REM to be executed by DOS, which is required for file operations.
+REM GET commands after these will retrieve bytes from the file.
+
+ 30  PRINT  CHR$ (4),"OPEN INPUT"
+ 40  PRINT  CHR$ (4),"READ INPUT"
+
+REM The "main loop".
+REM Builds string S$ from characters read from the input file. When a carriage
+REM return (13 in ASCII) is encountered, the line has ended and is ready to be
+REM parsed.
+REM `GET D$` is used to discard every other character in the file. Some quirk
+REM of the serial transfer placed carriage returns between each byte, so these
+REM need to be removed.
+
+ 100 S$ = ""
+ 110  GET C$
+ 115  GET D$
+ 120  IF  ASC (C$) = 13 GOTO 200
+ 130 S$ = S$ + C$
+ 140  GOTO 110
+
+REM Convert the string to a number. If it becomes zero, then an empty string
+REM was parsed: the current elf's calorie count is complete (GOTO 300).
+REM Otherwise, add to the total and fetch the next string.
+
+ 200 V =  VAL (S$)
+ 210  IF V = 0 GOTO 300
+ 220 CURR = CURR + V
+ 230  GOTO 100
+
+REM Manually sort the CALS array, which stores the top five calorie counts.
+REM If CURR belongs at index I, the lower calorie counts are shifted down a
+REM place and CURR is inserted. This is followed by printing the top three
+REM calorie counts.
+
+ 300  FOR I = 0 TO 5
+ 310  IF CURR = CALS(I) GOTO 360
+ 320  IF CURR < CALS(I) THEN  NEXT I
+ 330  FOR J = 3 TO I STEP  - 1:CALS(J + 1) = CALS(J): NEXT J
+ 340 CALS(I) = CURR
+ 350  PRINT CALS(0),CALS(1),CALS(2)
+
+REM Reset the current calorie count, then begin reading the next elf's data.
+
+ 360 CURR = 0
+ 370  GOTO 100
+
+REM End-of-file reached. Close the file, and print the total of the top three
+REM calorie counts.
+
+ 900  PRINT  CHR$ (4),"CLOSE"
+ 910  PRINT CALS(0) + CALS(1) + CALS(2)
+ 920  END 
+