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+---- Thread: What's wrong with this code? (/showthread.php?tid=337)
What's wrong with this code? - LTee - 03-24-2011
Okay, this is driving me mad. :-D
I wrote a little routine to 'shuffle' the numbers 1 to 10 into an array, randomly. It's not exactly the best way of doing this but it was supposed to be a quick test. Regardless, it doesn't work. Or rather, it does work - the first time you run it. The second loop of the same code never completes and I can't decide if I found a bug or if I've made a mistake.
Here's the code:
Code:
dim levelMap(10) as UBYTE
randomize
for x = 1 to 10
cls
generateLevelMap()
for n = 1 to 10: print levelMap(n): next n
pause 0
next x
SUB generateLevelMap()
dim lm as UBYTE
dim lmPos as UBYTE = 0
'clear the map first
for lm = 1 to 10
levelMap(n) = 0
next lm
'debug code to print the map, to make sure it's empty
print
for lm = 1 to 10
print levelMap(n);",";
next lm
print
pause 0
'now fill it randomly
print
for lm = 1 to 10
do
'get a random position in the array
lmPos = int(rnd * 10) + 1
'debug code to print the number we randomly picked
print lmPos;",";
'debug code to print the array element if it ISN'T empty
if levelMap(lmPos) <> 0 then
print ink 2;levelMap(lmPos);",";
end if
loop until levelMap(lmPos) = 0
'write the current number into the empty random element
levelMap(lmPos) = lm
'debug code to show that we handled this number okay
print inverse 1;lm
next lm
pause 0
cls
END SUBI've stuck a load of debug info in there so that you can see what it's doing.
Basically it does this:
1. Clear the array to all zeroes
2. For each number, 1 to 10....
3. Look in a random array position to see if it's zero.
3a. if it isn't, loop around to 3 and try a different one
3b. if it is, write the number into that array position and move on to the next number
4. The result should be the numbers 1 to 10 in a random order in the array, after a variable number of iterations.
First run, no problem.
Second run, although the debug code shows that the array was cleared, the do...loop until loop never completes - by the time it's checking the array within that loop it contains the OLD values again, despite me having zeroed them out just a few seconds earlier.
Am I missing an obvious goof? :-D
Re: What's wrong with this code? - LCD - 03-24-2011
Code:
for lm = 1 to 10
levelMap(n) = 0
next lmMaybe if you change it to:
Quote:for lm = 1 to 10Then it will really put a zero in each position of the array.
levelMap(lm) = 0
next lm
Look also here:
Code:
for lm = 1 to 10
print levelMap(n);",";
next lmRe: What's wrong with this code? - LTee - 03-24-2011
Ha ha, you're right! What a clown I am. :-D
That'll teach me to copy/paste stuff from one file to another! Thanks, LCD!
Re: What's wrong with this code? - boriel - 03-24-2011
Another pending feature: a command-line flag to enforce the user to *declare* (DIM) any used variable. This way, the levelMap(n) should complain about undeclared "n" var (or 2 Variable not Found) ;-) Free Basic also has this feature. I will put it, but need to re-re-check everything in the 1.2.8 version which now seems to be relatively stable at the moment...
Re: What's wrong with this code? - LTee - 03-24-2011
I'd like that! That's not the first time I've tripped up because of a bad copy/paste, and occasionally I've forgotten to declare something entirely and ended up with a float when a ubyte would've done.
And I'd agree on 1.2.8, by the way - it seems to be working great for me!