I think that it will be easier to debug that is unless you don't create to big a mess with objects in the first place (yes you can do that).Originally Posted by audioinstinct
Anywhay if you will need any help with classes (class inheritence, method inheritance, property inheritance, getter and setter methods of properties, some data reusability with external classes and data forwarding) do let me know and I'll help as best as I can.
Well I've started to rewrite it, and now it fails at line 2. Weirdest error I've ever seen. Error code is 216 it says "program received signal sigsegv segmentation fault". I researched this and it seems to mean that my program is trying to refer to a memory address that it is not allowed to, but I have absolutely 0 idea why that is. Here's the code:
Edit: I've just tried to add a watch to certain points of the Grid before I get the error. It seems that the trouble is deeper than I thought. I get to the point where the class is created, and then it's all weird. If I set the watch like this: Grid[i,j].candidates then it says it is not a structure or union type, whatever the hell that means, and if I set the watch like this: Grid[i][j].candidates then, it tells me this "Can not access memory at 0xe". Wtf is going on here? P.S: I'm administrator on this computer, mine is the only user anyway, and it might be relevant, I'm using Windows 7 as OP system.Code:{$mode objfpc} {$m+} Program SudokuSolverObject; uses crt; type Cell=Class private Procedure Eliminate(cand:smallint); Procedure ReaarangeCandidates; Function BoxCalc(x,y:smallint):smallint; public x,y,box:smallint; boxnullx,boxnully:smallint; candidates: array[1..9] of smallint; num_of_candidates: smallint; solved:boolean; constructor create(a,b:smallint); procedure ClearRow(cand:smallint); procedure ClearColumn(cand:smallint); procedure ClearBox(cand:smallint); procedure Solve(cand:smallint); End; VAR Grid:array[1..9,1..9] of Cell; Completed:boolean; Constructor Cell.create(a,b:smallint); var i:smallint; Begin x:=a; y:=b; for i:=1 to 9 do begin candidates[i]:=i; end; box:=BoxCalc(a,b); //This function is defined before this in the code, I didn't include it because it's not related to the error at all num_of_candidates:=9; solved:=false; if box=1 then begin boxnullx:=1; boxnully:=1; end else if box=2 then begin boxnullx:=1; boxnully:=4; end else if box=3 then begin boxnullx:=1; boxnully:=7; end else if box=4 then begin boxnullx:=4; boxnully:=1; end else if box=5 then begin boxnullx:=4; boxnully:=4; end else if box=6 then begin boxnullx:=4; boxnully:=7; end else if box=7 then begin boxnullx:=7; boxnully:=1; end else if box=8 then begin boxnullx:=7; boxnully:=4; end else begin boxnullx:=7; boxnully:=7; end; End; Procedure Cell.Solve(cand:smallint); var i:smallint; Begin for i:=1 to 9 do begin candidates[i]:=0; {This is the line that gives me the error, but all the other changes do it too, I've tried to switch the orders, any change to any variable of the classes after they were created throws me this stupid error. I've tried adding "self." before the assignments too, it didn't help.} end; num_of_candidates:=1; solved:=true; candidates[1]:=cand; End; // I have all the other functions and procedures for the class defined as well, but they're not related to this problem. Procedure ReadGrid; var i,j:smallint; inp:string; act:smallint; err:smallint; Begin for i:=1 to 9 do begin Writeln('Please give me the clues of row # ',i, ' (0 means no clue)'); Readln(inp); for j:=1 to 9 do begin val(inp[j],act,err); Grid[i,j].create(i,j); //This works just fine, there is no error yet if act<>0 then //"act" has a valid value, I double-checked it in debug mode, it works fine. begin Grid[i,j].Solve(act); //This is the point where the program enters the procedure which gives the error end; end; end; End; BEGIN Writeln('Welcome to Sudoku solver!'); Readgrid; Readln; End.
Edit2: I've tried running this ridiculously easy program and it failed with the same BS so the problem is even deeper than I thought. Either I screw up the class definitions or it has to do something with the compiler...
Code:{$mode objfpc} {$m+} Program wtf; type testclass=class private datx:integer; public dat1:integer; dat2:integer; constructor create(d1,d2,dx:integer); end; Constructor testclass.create(d1,d2,dx:integer); Begin datx:=dx; dat1:=d1; dat2:=d2; End; Var what:testclass; i,j,k:integer; Procedure Whatthef(a,b,c:integer); Begin what.create(a,b,c); End; BEGIN Writeln('Give me the first variable'); Readln(i); Writeln('Give me the second'); Readln(j); Writeln('Give me the third'); Readln(k); Whatthef(i,j,k); Writeln('The first value was: ', what.dat1); Writeln('The second value was: ',what.dat2); Writeln('The third value was private'); Readln; End.
Last edited by audioinstinct; 04-01-2015 at 07:23 PM. Reason: addition
The problem lies in the way you are creating your classes.
Whenever you are creating classes you use next sytax:
So in your case you need to call:Code://ClassRefereneVar is variable trhrough which you will be accessing your class //MyClass is the name of the class you are creating ClassReferenceVar := MyClass.Create;
instead of:Code:Grid[i,j] := Cell.create(i,j); //Right approach
EDIT: Pepole usually add T prefix to class names (TCell insted of just Cell) so that they can be quicly distinguished between normal variables in code.Code:Grid[i,j].create(i,j //Wrong approach
Last edited by SilverWarior; 04-01-2015 at 10:25 PM.
Haha omg epic fail. Object Pascal 101, well thanks, I hate stupid mistakes like this, because I never guess the problem is something so simple. It runs fine now. I will continue to rewrite the original code with objects tomorrow, and see how it turns out. It's pretty weird though, pascal is always so strict with the syntax, and it allowed me to start the program like that. Basically this means the class it creates points to nothing, so it's no wonder it couldn't access the memory address, oh well, I guess I will get used to it, just takes some time.
Never a mistake is stupid... unless you do the same twice. We learn from mistakes, to do improved versions... in more spectacular failures!
That's a compiler problem. Never used FPC and not sure if Delphi is able to catch that kind of errors at compile time, I think it warns about uninitialized variables.
If you ever play with pointers, you are going to see weirder things for sure.
You can make same mistake with Delphi. It also took me quite some time to learn that.
Nof if I'm not mistake this is left in in Objective Pascal as backward compatibility to the verry first days of Objective Pascal when classes still didn't have capability to automatically initialize its own members (internal fields, variables, etc.).
I think I once sow a code that actually makes use of this to delay the initialization of some class members in order to speed up the creation process of the class itself.
But this is pactically not used nowadays becoouse you would usually want for your class to be the decendant of TObject class which provides you with some basic and comonly used functionality like class name property with which you can determine the class type at runtime without the use of extended RTL, then quckly creating of new instances of that particular class etc.
So before I write the code for this method I was thinking I'd ask for a bit of advice here. I don't want to rewrite it later, and my approach is pretty brutal, I get this feeling that there just must be a more efficient way...
First, I will explain the concepts of Hidden Pairs, in Sudoku theory. This is a really simple one.
It means that in a house(row, column or box) TWO candidates both have an incidence of two in that house, and both candidates reside in the same two cells. Currently, there may be other candidates too in these cells.
What does this mean? Well, think about it... We know that both candidates must be somewhere inside that house and we know that each candidate can only occur once.
Let's say we're in row #3, and we have the following situation:
Candidates for position #4: 3 ,4, 6 ,7. Candidates for position # 7: 3 ,4,5,6,8. There is no other cell in this row that contains 3 or 6 as a candidate.
Let's assume that the cell at position #4 is not a 3 or a 6. What does this mean? Well it means that both 3 and 6 would have only one possible place in this row, and that is at position #7. Since a cell can only have one value at a time, we can conclude that the cell at position #4 must be either a 3 or a 6. We can say the same about the cell at position #7.
Now my question is, what do you think would be the most efficient way of finding these? What I have done certainly does work, but I am sure there is an easier or more efficient way. This is how it works right now:
As you can see it is a mass amount of loops going on here, and it looks pretty ugly.Code:Procedure Find_Hidden_Pairs; var i,j:smallint; // i always marks a row and j always marks a column in my code box:smallint; //boxes are numbered from 1-9 from left to right, up to down. count1,count2:smallint; //These are the variables for the possible candidates. candidate:smallint; //This will be used in a short loop to determine which candidates can be eliminated. TargetCell1,TargetCell2:Cell; //These will be the cells where an elimination will occur Begin TargetCell1:=Cell.create(1,1); TargetCell2:=Cell.create(1,1); //It doesn't matter that yet they have the same properties, I just want to initialize them. for count1:=1 to 9 do begin //Check for Rows for i:=1 to 9 do begin if ( Candidate_Count(count1,i,'row')=2 ) then //Function Candidate_Count(candidate,housenumber:smallint;housetype:string):smallint returns how many candidates exist in a house. begin for count2:=1 to 9 do begin if (count1<>count2) and (Candidate_Count(count2,i,'row')=2) then //We don't want the program to find a 3 that pairs with 3... begin TargetCell1.x:=0; TargetCell2.x:=0; for j:=1 to 9 do begin if ( Candidate_Exists(i,j,count1) )and (Candidate_Exists(i,j,count2) ) then begin {Function Candidate_Exists(row,column,candidate:smallint):boolean Checks if a cell has a possible candidate. This is necessary because it is possible that 2 candidates only have 2 instances but they reside in more than 2 cells. Such as in a row: position#1: 1,3 position#2: 5,3 position#3: 4,1. And the other cells don't have 3 or 1 as candidates, now obviously these don't form pairs} if TargetCell1.x=0 then begin TargetCell1.x:=i; TargetCell1.y:=j; end else begin TargetCell2.x:=i; TargetCell2.y:=j; end; end; end; if TargetCell2.x<>0 then begin for candidate:=1 to 9 do begin if (candidate<>count1) and (candidate<>count2) then begin Grid[TargetCell1.x,TargetCell1.y].Eliminate(candidate); Grid[TargetCell2.x,TargetCell2.y].Eliminate(candidate); end; end; end; end; end; end; end; //End of Row Checks {Here would come the column checks and box checks, I won't include because it follows the exact same procedure the box is only slightly different... sooo....} //Check for Columns //Check for Boxes end; TargetCell1.done; TargetCell2.done; End;
Right now it starts with candidate 1 on each row and if it finds a row where it occurs twice it checks the row for another candidate from 1-9 that occurs twice and if they happen to form a pair then it eliminates the other possibilities, if they don't happen to form a pair, then it will search for another second candidate, and so on, and then it will go to the next row, and if it doesn't find any rows for that candidate then it goes to columns and boxes and then it starts all over again with a starting candidate for 2, and goes on until the pair 9,8 is checked for box 9.
There should be a recursive way or I don't know, anything that won't cause it to go through 5 or 6 for loops just to check one row for 2 candidates. It seems way overkill. Anyone has an idea how can I make this more simple?
Last edited by audioinstinct; 05-01-2015 at 01:52 PM.
I apologize for nitpicking but it must be stressed that 'Objective Pascal' (A pascal equivalent to Objective-C for using Apple Objective-C interfaces) is something quite different to 'Object Pascal' (What everybody is thinking about)
--
I was going to write a Monte Carlo Sudoku solver for you to demonstrate the principal (The basic premise of a Monte Carlo simulation is to converge upon an answer to a problem by using random sampling (or more generally to determine the probability distribution of an unknown value which in turn can be used to estimate the true value))
However a search online provides an excellent approach to this technique that you can investigate : http://www.lptmc.jussieu.fr/user/talbot/sudoku.html
Before you get your feet too wet, a good learning exercise for the Monte Carlo method is to write a program to estimate the value of Pi by using either the ratio of a circle to a square with a length equal to the diameter of the circle or the more interesting technique which is to code a virtual buffon's needle simulation and measure the ratio of needle samples that cross lines to those that fall between.
One of the most interesting things about Monte Carlo simulations is that they become more accurate (or converge more quickly depending on the class of problem) the more 'random' your random generator is. By using a true random source of a uniform distribution you'll converge on answers more quickly or provide more accurate estimates than if you use the standard pseudo random generator provided in programming libraries. I had fascinating results (Buffon's needle Pi estimator) using a stream of true atomic random numbers as seeds for a pseudo generator. I even gained a whole decimal place of accuracy by feeding in random mouse movements (ensuring you get a good uniform distribution of samples before you re-seed - distribution of random generators and pseudo random generators in general can differ wildly, many are *not* uniform. I know that the FPC random functions are uniformly distributed but I can't vouch for Delphi)
It's truly mind blowing when you get it and it's a lot simpler than it sounds. Plus how cool is it to say you solve sudoku puzzles using the same technique that's used to model nuclear explosions?
Last edited by phibermon; 05-01-2015 at 06:35 PM.
When the moon hits your eye like a big pizza pie - that's an extinction level impact event.
Hey, thanks for the replies and all the help, guys. I had to take a pause from continuing the program, I am having some difficult exams, I will continue when I'm done with them and keep this thread updated.
Peace.
Reply With Quote
Bookmarks