Lottery numbers & non repeating values tool
Post by michaelgallup on Mar 28th, 2016, 08:42am
This is the Canadian LOTTO MAX.. there are 7 numbers out of 49 that you must pick.
This program should be up to everyones standards.
1) no use of GOTO or GOSUB
2) no ancient coding ways.
3) it was built from the ground up
4) it has key detection so you can roll for more numbers
5) it has a tool that prevents repeating values ( this took a lot of testing)
( I hope you like the tool that checks for repeating values. It may be useful for other things)
Please let me know if there is any improvements I should make with my coding.
Thankyou.
Code: DIM x%(7) CLS:PROC_newnumbers REPEAT key$="" key$ =INKEY$(1) IF LEN(key$) = 1 THEN IF key$="r" OR key$="R" THEN PROC_newnumbers ENDIF UNTIL key$="q" OR key$="Q" PRINT "done" END DEF PROC_newnumbers CLS PRINT "Here is 7 numbers for Lotto Max" REPEAT FOR t=1 TO 7 x%(t)=RND(49) NEXT t PROC_comparray(7) UNTIL cond$="cleared" FOR t=1 TO 7 PRINT x%(t) NEXT t PRINT "Press R or r for more numbers or Press Q or q to quit" ENDPROC DEF PROC_comparray(n) cond$="cleared" nex=1 FOR cou=1 TO n FOR co=nex TO n IF cou<>co THEN IF x%(cou)=x%(co) THEN cond$="duplicate" NEXT co nex=nex+1 NEXT cou ENDPROC
Re: Lottery numbers & non repeating values tool
Post by Richard Russell on Mar 29th, 2016, 10:18am
on Mar 28th, 2016, 08:42am, michael gallup wrote:| Please let me know if there is any improvements I should make with my coding. |
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Since you asked I'm afraid that there are several things that could be improved.
The most fundamental problem is that you have failed to adhere to the concept of information hiding which is so important in modern computing (and crucial for a general-purpose routine that might go into a library). Here are some examples in PROC_comparray():
The array itself is global, forcing the user to give it a specific name x%(). And what if he wants to check two or more different arrays?!
The result is passed back in a global cond$. This is bad practice (reminiscent of an old-fashioned GOSUB). Since the routine returns a single Boolean result (either the array has duplicates or it doesn't) a function would be a better choice than a procedure here.
The temporary variables used within the routine (nex, cou and co) are globals and could therefore corrupt a variable of the same name used elsewhere in the program!
Another, unrelated, problem is that your routine assumes that the array indices start from 1, but what if the user wants to check duplicates in an array that starts at index 0?
I wonder if you ran the Cross Reference utility on your program, since this would have drawn attention to some of these issues (but you mustn't rely on it to do so).
As an example of how it could be improved, here is a re-written version:
Code: DEF FN_checkduplicates(x%(), i%, n%) LOCAL C%,I%,J% IF n% <= i% THEN = FALSE FOR I% = i% TO n%-1 FOR J% = i%+1 TO n% IF x%(I%) = x%(J%) THEN C% = TRUE NEXT NEXT = C%
Take note of these salient points:
A function is used rather than a procedure.
The function returns a Boolean result FALSE or TRUE.
The array to be checked is passed as a parameter.
Both the starting and ending indices are passed as parameters.
The variables used within the function are declared as LOCAL.
Static integer variables are used where possible for speed and to reduce memory use.
If you are greatly concerned about performance, the function could bail out early as soon as a duplicate is found:
Code: DEF FN_checkduplicates(x%(), i%, n%) LOCAL C%,I%,J% IF n% <= i% THEN = FALSE FOR I% = i% TO n%-1 FOR J% = i%+1 TO n% IF x%(I%) = x%(J%) THEN C% = TRUE : EXIT FOR I% NEXT NEXT = C%
Even faster would be to do this, but some people don't like to see multiple exit points from a function:
Code: DEF FN_checkduplicates(x%(), i%, n%) LOCAL I%,J% IF n% <= i% THEN = FALSE FOR I% = i% TO n%-1 FOR J% = i%+1 TO n% IF x%(I%) = x%(J%) THEN = TRUE NEXT NEXT = FALSE
Richard.
Re: Lottery numbers & non repeating values tool
Post by michaelgallup on Mar 29th, 2016, 11:06am
Thanks.. I will study function use and implement them into my future programs.
Re: Lottery numbers & non repeating values tool
Post by PatrickM on Apr 10th, 2017, 3:38pm
Quote:Even faster would be to do this, but some people don't like to see multiple exit points from a function:
Code: DEF FN_checkduplicates(x%(), i%, n%) LOCAL I%,J% IF n% <= i% THEN = FALSE FOR I% = i% TO n%-1 FOR J% = i%+1 TO n% IF x%(I%) = x%(J%) THEN = TRUE NEXT NEXT = FALSE
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This surprised me, I didn't know you could do that - I thought it would result in a 'Too many FORs' error, but now that I've tested it I see that would only be a problem on the BBC Micro and (I assume) other older versions of BBC Basic.
Re: Lottery numbers & non repeating values tool
Post by Richard Russell on Apr 10th, 2017, 4:10pm
on Apr 10th, 2017, 3:38pm, PatrickM wrote:| I didn't know you could do that - I thought it would result in a 'Too many FORs' error... |
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Possibly, but if so I think that behaviour is unique to the 6502 versions of BBC BASIC. As far as I know every other version, including later ones from the Acorn stable (e.g. ARM BASIC V), all of mine (including the 8-bit Z80 version) and Brandy allow you to abort from inside a FOR...NEXT - or any other variety of loop - like that.
Nevertheless EXIT FOR etc. (available in BB4W and BBCSDL) is generally preferable. Its omission from earlier versions of BBC BASIC is one of the few significant limitations of the language, in my opinion. It's understandable that it wasn't in the 8-bit versions but with hindsight it should have been added at the same time as WHILE...ENDWHILE and multi-line IF...ENDIF.
Richard.
Re: Lottery numbers & non repeating values tool
Post by MarsFS on Sep 1st, 2017, 04:39am
Here's another example of how it might be done using less loops and reduced redundant comparisons. The check for dupes FN gets called before assigning a new number to the array and printing is included in the main loop. Variables have been added to allow a different amount of numbers and number range.
Another nice addition would be to sort the numbers before printing.
Code: REM Lotto number generator max%=49 nums%=7 DIM x%(nums%-1) REPEAT PROC_newnumbers key$ =GET$ UNTIL key$="q" OR key$="Q" PRINT "Done" END DEF PROC_newnumbers LOCAL t,n CLS PRINT "Here is ";STR$(nums%);" numbers for Lotto Max:": PRINT FOR t=0 TO nums%-1 REPEAT n=RND(max%) UNTIL FNnodupes(n,t-1) x%(t)=n PRINT STR$(n);" "; NEXT t PRINT: PRINT PRINT "Press any key for more numbers, Press 'Q' to quit" ENDPROC DEF FNnodupes(n,c) LOCAL t IF c>-1 THEN FOR t=0 TO c IF n=x%(t) =FALSE NEXT ENDIF =TRUE
Re: Lottery numbers & non repeating values tool
Post by Leo on Sep 1st, 2017, 5:19pm
Here's a very simple version which does multiple lines and outputs numbers in order (without sorting).
Code: REM Simple Lottery. Multiple lines, output ordered. NMAX%=49 LMAX%=7 DIM N&(NMAX%) @%=&02 INPUT "How many lines", J% FOR I%=1 TO J% PROC_Line NEXT END REM Create and print a lottery line DEF PROC_Line LOCAL c%, i%, x% N&()=0 REPEAT x% = RND(NMAX%) IF N&(x%) = 0 THEN N&(x%) = x% c% += 1 ENDIF UNTIL c% = LMAX% FOR i%=1 TO 49 IF N&(i%) THEN PRINT " " i%,; NEXT PRINT ENDPROC
Re: Lottery numbers & non repeating values tool
Post by Richard Russell on Sep 1st, 2017, 8:35pm
on Sep 1st, 2017, 5:19pm, Leo wrote:| Here's a very simple version which does multiple lines and outputs numbers in order (without sorting). |
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Personally I dislike and distrust all solutions that rely on repeatedly choosing a 'random' number until it's not one of a previously chosen set (or repeatedly choosing a set of numbers until some condition is met).
I dislike it because the execution time is not predictable. Suppose one was using that technique to draw 52 cards from a pack; the last card drawn is already known (it's the only one left) but a 'repeat RND(52) until not already chosen' loop might have to repeat dozens or hundreds of times before that unique number is selected. Theoretically it could take an indefinitely long time.
I distrust it because it is not obvious 'by inspection' that the method is statistically sound. It probably is, but as I'm not a mathematician I can't be confident that it really is resulting in an unbiased selection (to the degree that the pseudo-random number generator allows, at least).
So I would always prefer a method that has a predictable execution time and guaranteed statistics, such as a well understood and documented shuffling algorithm (e.g. the Fisher-Yates or Knuth shuffle).
Richard.
Re: Lottery numbers & non repeating values tool
Post by MarsFS on Sep 1st, 2017, 10:20pm
Here's another version using a knuth shuffle with multiple lines and sorted and formatted output:
Code: REM Lotto number generator max%=49 nums%=7 DIM allNumbers(max%) DIM sorted(max%) REM Creat a fresh set of numbers FOR T%=1 TO max% allNumbers(T%)=T% NEXT REPEAT PROC_newnumbers key$ =GET$ UNTIL key$="q" OR key$="Q" PRINT "Done" END DEF PROC_newnumbers LOCAL T%,N%,C%,J%,A$ CLS PRINT "Lotto Number Picker" PRINT "-------------------" INPUT "How many lines (1-18): ", J% IF J%<2 OR J%>18 THEN J%=1 A$="is 1 line" ELSE A$="are "+STR$(J%)+" lines" ENDIF CLS PRINT "Here ";A$;" of ";STR$(nums%);" numbers for Lotto Max:": PRINT FOR C%=1 TO J% REM randomly shuffle the numbers FOR T% = max% TO 2 STEP -1 SWAP allNumbers(T%),allNumbers(RND(T%)) sorted(T%)=0 NEXT sorted(1)=0 REM choose a random set and sort N%=RND(max%-nums%+1) FOR T%=N% TO N%+nums%-1 sorted(allNumbers(T%))=allNumbers(T%) NEXT REM print sorted list PRINT "Line ";RIGHT$("0"+STR$(C%),2);": "; FOR T%=1 TO max% IF sorted(T%) PRINT RIGHT$(" "+STR$(sorted(T%)),2);" "; NEXT PRINT NEXT PRINT:PRINT "Press any key for more numbers, Press 'Q' to quit" ENDPROC
Re: Lottery numbers & non repeating values tool
Post by Richard Russell on Sep 2nd, 2017, 11:15am
on Sep 1st, 2017, 10:20pm, MarsFS wrote:| Here's another version using a knuth shuffle with multiple lines and sorted and formatted output |
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Nice, and works without modification on both BB4W and BBCSDL!
For my own interest I ran some tests on how many calls to RND(52) might be necessary before a specific unique number is returned. The answer seemed to be that needing to call it more than 900 times is not that unlikely (the highest I saw was 996)! Obviously typically it will be fewer, but it illustrates the uncertainty in execution time that can arise from using that technique.
Richard.
Re: Lottery numbers & non repeating values tool
Post by Leo on Sep 2nd, 2017, 4:00pm
Although I can't disagree with the logic behind "run time is unpredictable" - the lottery case here is a complete frippery. It's just a "throwaway" toy.
Of course I wouldn't use the technique I did for anything approaching any seriousness but I stand by my choice for the lottery case because..
a) It's a complete frippery.
b) The program is very short.
c) We're only selecting ANY 7 numbers from 49 so there's no chance of this taking forever.
d) The quality of the random numbers is irrelevant because any 7 will have an equal chance of winning.
I also ran some trials (a lot).
The maximum number of lookup clashes in any single line was 6 - sounds a lot.
However, in creating 10000 lottery lines a repeat lookup was necessary in 6.7% of cases - no problem.
Henceforward I will use the dates of my children's birthdays to derive (winning) lottery lines. 
Re: Lottery numbers & non repeating values tool
Post by Richard Russell on Sep 2nd, 2017, 4:43pm
on Sep 2nd, 2017, 4:00pm, Leo wrote:| I stand by my choice for the lottery case because... |
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That's fine, with those qualifications. The trouble is that people may adapt the code for other applications without appreciating its limitations (for example they may come upon it years later as the result of a search).
My experience is that there is widespread misunderstanding about pseudo-random numbers and statistics, and although it's unlikely that anybody would use BBC BASIC for an online casino program, or something like that, it's not impossible.
Several years ago I wrote this article at the Wiki to draw attention to some of the pitfalls. It includes simple lottery draw and card shuffling programs. It's out of date to the extent that BBC BASIC no longer uses the value of TIME as a seed.
Richard.
Re: Lottery numbers & non repeating values tool
Post by Leo on Sep 2nd, 2017, 9:00pm
Thanks for that link Richard - very good article.
Although I'm gradually working my way through the info in the wiki, I admit I haven't read that one before. Everybody who uses BB4W should go and rummage through the wiki - there's so much excellent information in there.
I use CryptGenrandom a lot for 'professional' use. I think I posted something here that used it a short time ago - but I don't remember what right now. (My memory ain't what it used to be).
Thanks again for the info.