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Help with for loops and strings when loading files.


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#1 Monkey_Missile   Members   -  Reputation: 104

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Posted 20 February 2012 - 08:05 PM

With C++ and SDL I'm having a bit of a brain fart remembering and finding the syntax for what I'm trying to do. I have a for loop in a function that is loading files into an array. (char* file, int number) are the two parameters of the function where file is the first part of the file name and number is the number of files. I have the files named as such:

example0.png
example1.png
example2.png

The code for the for loop is as follows:

for (int i = 0; i < number; i++)
	{
		Array[i] = OnLoad((file) + i + ".png") ;
	}

OnLoad is a function I have for loading files which works independently of this. My question is when I pass the parameters "example" and "3" to the function and thus this for loop how do I have the above translate it into "example0.png" and so on.

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#2 Washu   Senior Moderators   -  Reputation: 4531

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Posted 20 February 2012 - 08:08 PM

You're using C++, so you should be using std::string, but anyways...
std::ostringstream ss;
ss<<file<<i<<".png";
std::string filename = ss.str();
ostringstream is located in the <sstream> header.

In time the project grows, the ignorance of its devs it shows, with many a convoluted function, it plunges into deep compunction, the price of failure is high, Washu's mirth is nigh.
ScapeCode - Blog | SlimDX


#3 zacaj   Members   -  Reputation: 643

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Posted 20 February 2012 - 08:26 PM

You're using C++, so you should be using std::string, but anyways...

std::ostringstream ss;
ss<<file<<i<<".png";
std::string filename = ss.str();
ostringstream is located in the <sstream> header.

Is there any reason to do this vs:
OnLoad(string(file) + '0'+i+ ".png")


#4 Washu   Senior Moderators   -  Reputation: 4531

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Posted 20 February 2012 - 08:30 PM

THe result of '0'+i is an integer. an integer + std::string is not a valid operator combination (there is no appropriate overload).

In time the project grows, the ignorance of its devs it shows, with many a convoluted function, it plunges into deep compunction, the price of failure is high, Washu's mirth is nigh.
ScapeCode - Blog | SlimDX


#5 Monkey_Missile   Members   -  Reputation: 104

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Posted 20 February 2012 - 08:33 PM

Washu's suggestion worked, thanks :) Now to get my rendering function to work. I'll be back if I get stuck again.

#6 zacaj   Members   -  Reputation: 643

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Posted 20 February 2012 - 08:40 PM

You could always cast it. In my opinion that'd still look a lot better than instantiating a whole new class just to concatenate a string

#7 Washu   Senior Moderators   -  Reputation: 4531

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Posted 20 February 2012 - 08:41 PM

And the instant i is no longer a number between 0 and 9 you would immediately fail. Btw, the character immediately after '9' is ':', which as you can imagine doesn't work out so well in the middle of a filename.

In time the project grows, the ignorance of its devs it shows, with many a convoluted function, it plunges into deep compunction, the price of failure is high, Washu's mirth is nigh.
ScapeCode - Blog | SlimDX


#8 rip-off   Moderators   -  Reputation: 7706

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Posted 21 February 2012 - 03:44 AM

You could always lexical_cast<> it, which would hide the details of the conversion (as we don't really care about them in this case).

#9 Washu   Senior Moderators   -  Reputation: 4531

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Posted 21 February 2012 - 04:20 AM

You could always lexical_cast<> it, which would hide the details of the conversion (as we don't really care about them in this case).


True, if he's using boost. If he's using a modern compiler AND C++0x he might have access to std::to_string functionality as well.

However, this is For Beginners, so the best answer is usually the one that requires the fewest number of "If you have X and version of X is greater than Y" or "if you have X installed and configured correctly", which in this case happens to be stringstream.

In time the project grows, the ignorance of its devs it shows, with many a convoluted function, it plunges into deep compunction, the price of failure is high, Washu's mirth is nigh.
ScapeCode - Blog | SlimDX





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