diff --git a/applesoft/nfs/general/04_avoid_integer_variables.md b/applesoft/nfs/general/04_avoid_integer_variables.md index c7c88a6..68b1e4e 100644 --- a/applesoft/nfs/general/04_avoid_integer_variables.md +++ b/applesoft/nfs/general/04_avoid_integer_variables.md @@ -129,21 +129,27 @@ It applies for dimensioning arrays with `DIM` (e.g. `N=123.456: DIM A(N)` works) It applies to indices of arrays. It means that an array like `M(X, Y)` representing for example the player's X-Y position in a maze can be used without worrying about `X` and `Y` being integers. -Strangely, it also works with `GOTO` and `GOSUB`, and though you'll probably never do it because you cannot use arithmetic expressions after `GOTO`/`GOSUB`, know that `GOTO 100.123456` works, as long as you have a line 100 in your code of course. +It also works with `GOTO` and `GOSUB` but for another reason. Applesoft expects numbers after a `GOTO/GOSUB` instruction and once it finds a character that is not numeric, it will ignore every other character and just do his `GOTO/GOSUB`. -But more interestingly, it works with `ON/GOTO-GOSUB` (*) This means you can do this: +This means that +- `GOTO 100.123456` works but also +- `GOTO 100 THIS WON'T BE PARSED`, + +as long as you have a line 100 in your code of course. + +But more interestingly, you don't need to use integer values with `ON/GOTO-GOSUB` (*). This means you can do this: ```basic ON RND(1)*10 GOTO 100,200,300,400 ``` -and `INT` it totally superfluous ! +Using `INT` here is totally superfluous ! (*) As we'll see in another chapter, ON/GOTO is faster than a sequence of multiple IF/THEN conditions and is the preferred method when your code needs branching. -This is very useful for random events, AI decisions, or simply branching your code based on a calculation, for example you could scale a value and react accordingly: +This is very useful for random events, AI decisions, or simply branching your code based on a calculation, for example you could scale a value and react accordingly without worrying about your scaled value being an integer: ```basic 10 D=47: REM DISTANCE COVERED SO FAR 20 M=100: REM MAX DISTANCE -30 Q=25: REM DIVIDER (100/25 = 4 DIFFERENT MSGS + 1) +30 Q=25: REM DIVIDER (100/25 = 4 DIFFERENT MSGS + 1 EXTRA) ... 100 ON D/Q GOTO 120, 130, 140, 150 : REM NO NEED TO USE INT HERE ! 110 PRINT "GOOD LUCK !": GOTO 160: REM 0-24 @@ -213,19 +219,19 @@ But: - `HTAB EX%: PRINT "X"` or - `PLOT EX%, EY%` or - `HPLOT EX%, EY%` or - - `(X)DRAW E AT EX%,EY%`. + - `(X)DRAW E AT EX%,EY%` or + - your own technique, but you still need to access `EX%` and `EY%` - you need to check if the player's position is the same as the enemy's - `IF EX%=X AND EY%=Y THEN ...` - you need to erase the enemy on the next loop iteration, meaning - - you might store the enemy's previous position in another set of variables + - you might need to store the enemy's previous position in another set of variables - `XE=EX%: YE=EY%` (no need to use integer variables like `XE%` or `YE%` since the conversion is already done) - you'll do another call to `HTAB+PRINT`, `PLOT`, `HPLOT`, `(X)DRAW` - you might need to check if the enemy was hit by the player's projectile - `IF EX%=PX AND EY%=PY THEN ...` - etc. -Every time you use `EX%` (and `EY%`) you'll lose 200-350 cycles and after 3-5 times, using an real variable is a better choice. - +Every time you use `EX%` (and `EY%`) you'll lose 200-350 cycles and after 3-5 times, using a real variable is a better choice. ## 🍎 Recommendations