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[Stargrasper]

So, we're doing Rock, Paper, Scissors in C++, and my teacher says that my random number generator will always generate the same thing, but I can't get it to do it. Could someone look this over for me, please?

Spoiler (click to show/hide)

Code: [Select]

//always seeding the same. Fix this.
int computerchoice()
{
           int computer;
           unsigned seed = time(0);
           srand(seed);
           computer = 1+rand()%3;
 return computer;         
}

Funny thing is, I was showing someone a little C++ a couple days ago and spent fifteen minutes writing rock, paper, scissors just to show that person an example of basic C++.

I get the feeling this is going to be a busy semester...oh well, I'll get to learn how to create my own programming language this semester.  That should at least be interesting.

[GlyphGryph]

Any idea what sort of language you'll be building/want to build?

[Nadaka]

So, we're doing Rock, Paper, Scissors in C++, and my teacher says that my random number generator will always generate the same thing, but I can't get it to do it. Could someone look this over for me, please?

Spoiler (click to show/hide)

Code: [Select]

//always seeding the same. Fix this.
int computerchoice()
{
           int computer;
           unsigned seed = time(0);
           srand(seed);
           computer = 1+rand()%3;
 return computer;         
}

Funny thing is, I was showing someone a little C++ a couple days ago and spent fifteen minutes writing rock, paper, scissors just to show that person an example of basic C++.

I get the feeling this is going to be a busy semester...oh well, I'll get to learn how to create my own programming language this semester.  That should at least be interesting.

It can be fun, but it is very tedious. I used concepts from programming language and compiler design to write a very limited grammar for creating expressions for rolling dice, but that has been the extent of my use of that knowledge.

[Valid_Dark]

I rewrote the trajectory part as a function but for some reason it's breaking the game and I can't figure out why,

Spoiler (click to show/hide)

I made the function

void Traject (int max, int xoffset, int yoffset, double a, double b, spriteSheet spritename,SDL_Surface*& screen, int spin, int counter, int state)
{
int x, y;
x = ((max/spritename.speed)*counter)+xoffset;
y = (a*((x-xoffset)*(x-xoffset))+(b*(x-xoffset))+yoffset);
drawSprite (spritename, screen, spin, x, y);
}

so instead of

ball1x = ((360/ball1.speed)*counter)+10;
ball1y = (0.00771605*((ball1x-10)*(ball1x-10)))+(-2.77778*(ball1x-10))+353;
drawSprite(ball1, screen, spin, ball1x, ball1y);
counter--;
                if (ball1y>350&&ball1y<370&&leftHandPos==1&&ball1x<250)
                    {ball1.state = 2;
                    counter = 0;
                    random = ((rand()%3)+1);}

I should be able to write

        Traject(360,10,353,0.00771605,-2.77778,ball1,screen,spin,counter);
        counter--;
                if (ball1y>350&&ball1y<370&&leftHandPos==1&&ball1x<250)
                    {ball1.state = 2;
                    counter = 0;
                    random = ((rand()%3)+1);}

but for some reason it never does the if statement afterwards when using the function way, but it does when it's written out.
am I missing something?

[Telgin]

Maybe I'm missing something, but... when you're moving that to a function, you're no longer setting ball1x and ball1y before testing them in the if statement.  Without seeing the rest of the code, that's my guess.

[Valid_Dark]

thank you,

this forum is a lifesaver, really, thank you everyone for how much help you've all given me so far.

how would I go about doing that?
I don't know how to refer to variables set inside a void function outside of that void function.

[Gatleos]

Normally, when variables are passed into a function a copy is made. Anything you do to the variables inside the function is done to the copy. If you want to affect the variables directly, you should pass them in by reference.

Code: [Select]

Traject(int ball1x,int ball1y)
{
     ball1x++;
     ball1y++;
}In this function, the variables ball1x and ball1y are passed in normally. When you increment them, you are only incrementing the copy. The variables outside the function are unchanged.

Code: [Select]

Traject(int &ball1x,int &ball1y)
{
     ball1x++;
     ball1y++;
}In this function, the two variables are passed in by reference; notice the ampersand (a.k.a. demon sign) before the variable names in the parameter list. The changes made to the two variables here affect the "real" variables, rather than a copy.

So, just pass the ball1x and ball1y variables into the function by reference, and the code you posted should work.

[Valid_Dark]

kk thanks, ya I remember that now,  I had a hard time understanding that part of my book, but you just cleared up any questions I had about it.
I had deleted all the work I had done on converting the trajectories to functions since was having trouble with it (back before you gave such wonderful assistance) right now I'm writing the score and combo system, almost done with it, then going to go back and re-write the traject function then add the second ball.
I had to learn a little C for writing the scoring system, since it is soo much better at writing int / string combos, instead of learning stringstream which i tried for a while but was a nightmare.

[Siquo]

IMHO, you should make a class Ball that has an x, y and maybe even trajectory information. This'll make it easier to have multiple balls as well.

[Valid_Dark]

Honestly I should have learned more c++ before jumping headfirst into SDL,
I was only on page 400 or so of my 1500 c++ book,
never got to the section that covered classes
although I'm considering moving the x and y positions to part of the struct
so I could do ball1.x and ball1.y
but it wouldn't really make too much of a difference, I wouldn't mind declaring each of the balls x and y's and ints
since there would only be 4 or 5 balls max.
I recently moved ballspeed and spinspeed out of that struct and made them global variables, since i'd never have them going different speeds.  working on graphics for score multipliers and misses right now.

[Telgin]

I had to learn a little C for writing the scoring system, since it is soo much better at writing int / string combos, instead of learning stringstream which i tried for a while but was a nightmare.

So you prefer c-style strings to C++'s string class(es)?  You might want to reconsider this, the plain ol' string class (not stringstream) abstracts away a lot of the headaches and errors with c-style strings.

Of course, if what you're doing is dirt simple and / or using on string constants, it's not a big deal and might be overkill.

[Valid_Dark]

no no no, don't get my wrong, I love the c++ string class,
but for SDL_ttf, in order to print any text to a surface it has to be in const char* type format.
I want to print a string and an int, that increases every so often "score"

with C this is as easy as

char charscore[15];
sprintf( charscore, "Score : %04d", score );

    score_ = TTF_RenderText_Solid( font, charscore, textColor );
    SDL_BlitSurface( score_ , NULL , screen , &scorepos );

I have no idea how to do this in C++, but I think it would be something along these lines

std::stringstream sstr;
sstr << my_int;
std::string str1 = sstr.str();

std::string str2 = boost::lexical_cast<std::string>(my_int);

which I was never able to get to work,
and that is just for the int to const char* conversion.

for everything else though c++ strings are the way to go.

[kaijyuu]

stringvariable.c_str() will convert your string variable into a c string to pass as the function argument. No need to mess with c strings otherwise.


Also, if you add "using namespace std" to the top of the file you can get rid of all those std:: prefixes. Unless you're using a different namespace, of course.

[Aqizzar]

Getting back into my roguelike for a general efficiency rebuild, I painlessly converted my MapGenerator, InterfaceObject, and MainScreen into static classes, so I can easily reference them from anywhere.  That's swell.

However, some of you who looked at my code mentioned that ConsoleKey data can be used in a switch statement?  Compiler says otherwise, that switches can only interpret primitives, which I recall is why I made a separate Interface to contain the gigantic if-else ladder I built to reinterpret ConsoleKey data as a byte to be passed to a switch statement.  Which is certainly duplication of effort, but with the Interface turned static I can use it anywhere and make some applications with it.

[nenjin]

I just wanted to add thanks for the references explanation. You feel really sheepish asking people who know what they're doing in coding fundamental questions like that, but sometimes that's the building block you need to move forward. You just need to hear it as plainly as possible.