string::size_type

Mark Rodgers · 2012-10-11T15:32:08

One of the example programs in my C++ book ;) I'm not really understanding this completely... I kinda understand how it is working but there are a few things that are confusing me.. Such as string::size_type. The book said that it returns the size of something (derp) but i tried outputting the result and it was like a bunch of random number. I didn't count but it was probably around 8 random numbers, for example: 35694625. I don't understand how that gets returned if it says it gets the size of something? o.o #include <iostream> #include <string> using std::cin; using std::endl; using std::cout; using std::string; int main() { cout << "Please enter your first name: "; string name; cin >> name; const string greeting = "Hello, " + name + "!"; int pad; cout << "Enter the desired amount of padding: "; cin >> pad; const int rows = pad * 2 + 3; const string::size_type cols = greeting.size() + pad * 2 + 2; cout << endl; for (int r = 0; r != rows; ++r) { string::size_type c = 0; while (c != cols) { if (r == pad + 1 && c == pad + 1) { cout << greeting; c += greeting.size(); } else { if (r== 0 || r == rows - 1 || c == 0 || c == cols - 1) cout << "*"; else cout << " "; ++c; } } cout << endl; } system("pause"); return 0; }

EddieV223

1,840

October 11, 2012 07:23 AM

SIZE_T just returns a integar or length of bytes for the string. SIZE_T is the same function of sizeof(). SIZE_T just stores the integar length of a string or what not.

SIZE_T StringLength; string Greeting = "Hello, I'm George!"; StringLength = sizeof(Greeting); cout << StringLength;

As you see the SIZE_T is a typdef that stores the integer of length. Where as sizeof function returns the length of the string Greeting.

std::string varString = "Hello World";
unsigned int size = sizeof(varString);
sizeof DOES NOT RETURN THE SIZE OF THE STRING INSIDE THE STD::STRING

It returns the size of the string class. The string class uses dynamic memory to store cstrings. So only the pointer is counted as well as any other members. If you want the size of an std::string you use .size();

If this post or signature was helpful and/or constructive please give rep.

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Paul C Skertich

805

October 11, 2012 02:08 PM

SIZE_T just returns a integar or length of bytes for the string. SIZE_T is the same function of sizeof(). SIZE_T just stores the integar length of a string or what not.

SIZE_T StringLength; string Greeting = "Hello, I'm George!"; StringLength = sizeof(Greeting); cout << StringLength;

As you see the SIZE_T is a typdef that stores the integer of length. Where as sizeof function returns the length of the string Greeting.

First of all

http://www.cplusplus.com/reference/clibrary/cstring/size_t/

http://msdn.microsoft.com/en-us/library/4s7x1k91%28v=vs.71%29.aspx

there is size_t; and plus sizeof() returns bytes of characters. Rather it be a sturct, a class or whatever.

I helped out and that's it.

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Paul C Skertich

805

October 11, 2012 02:12 PM

[quote name='SIC Games' timestamp='1349931097' post='4988961']
SIZE_T just returns a integar or length of bytes for the string. SIZE_T is the same function of sizeof(). SIZE_T just stores the integar length of a string or what not.

SIZE_T StringLength; string Greeting = "Hello, I'm George!"; StringLength = sizeof(Greeting); cout << StringLength;

As you see the SIZE_T is a typdef that stores the integer of length. Where as sizeof function returns the length of the string Greeting.

std::string varString = "Hello World";
unsigned int size = sizeof(varString);
sizeof DOES NOT RETURN THE SIZE OF THE STRING INSIDE THE STD::STRING

It returns the size of the string class. The string class uses dynamic memory to store cstrings. So only the pointer is counted as well as any other members. If you want the size of an std::string you use .size();
[/quote]

sizeof returns the length in bytes of a char. - whether it be a array or what not. Whatever - I was trying to help out; screw that idea.

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L. Spiro

25,818

October 11, 2012 03:01 PM

there is size_t; and plus sizeof() returns bytes of characters. Rather it be a sturct, a class or whatever.

“string” is a structure, so sizeof() returns the size of that structure, not the size of the string it manages.
If it was instead:
const char szString[] = "Hello fellow citizens.";
Then sizeof() would return the number of characters, including the terminating NULL.

screw that idea.

I supported you on SIZE_T but I feel less sorry for you after you posted this.

L. Spiro

I restore Nintendo 64 video-game OST’s into HD! https://www.youtube.com/channel/UCCtX_wedtZ5BoyQBXEhnVZw/playlists?view=1&sort=lad&flow=grid

swiftcoder

18,997

October 11, 2012 03:01 PM

sizeof returns the length in bytes of a char. - whether it be a array or what not. Whatever - I was trying to help out; screw that idea.

You are, unfortunately, blatantly wrong on this count.

sizeof() returns the correct size for the given type, or the correct length of a statically allocated array. std::string uses dynamically allocated memory to store the string contents, so sizeof() will not see that memory.

#include <string>

#include <cassert>

int main() {

    std::string A = "Hello, World!";

    std::string B = "Hi";



    assert( sizeof(A) == sizeof(B) );

}

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Paul C Skertich

805

October 11, 2012 03:12 PM

[quote name='SIC Games' timestamp='1349964519' post='4989104']
there is size_t; and plus sizeof() returns bytes of characters. Rather it be a sturct, a class or whatever.

“string” is a structure, so sizeof() returns the size of that structure, not the size of the string it manages.
If it was instead:
const char szString[] = "Hello fellow citizens.";
Then sizeof() would return the number of characters, including the terminating NULL.

screw that idea.

I supported you on SIZE_T but I feel less sorry for you after you posted this.

L. Spiro
[/quote]

Watever, dude. Seriously, all I hear is "IM WRONG" "I AM WRONG" from all you people on here. So, whatever. Have a good day; dude.

Game Engine's WIP Videos - http://www.youtube.com/sicgames88
SIC Games @ GitHub - https://github.com/SICGames?tab=repositories
Simple D2D1 Font Wrapper for D3D11 - https://github.com/SICGames/D2DFontX

Paul C Skertich

805

October 11, 2012 03:13 PM

[quote name='SIC Games' timestamp='1349964757' post='4989106']
sizeof returns the length in bytes of a char. - whether it be a array or what not. Whatever - I was trying to help out; screw that idea.

You are, unfortunately, blatantly wrong on this count.

sizeof() returns the correct size for the given type, or the correct length of a statically allocated array. std::string uses dynamically allocated memory to store the string contents, so sizeof() will not see that memory.

#include <string>

#include <cassert>

int main() {

	std::string A = "Hello, World!";

	std::string B = "Hi";



	assert( sizeof(A) == sizeof(B) );

}

[/quote]

Yeah you too have a good day, keep on warning people; bro! Cause you're cool like that.

Game Engine's WIP Videos - http://www.youtube.com/sicgames88
SIC Games @ GitHub - https://github.com/SICGames?tab=repositories
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L. Spiro

25,818

October 11, 2012 03:21 PM

I have been wrong too; it is all about how you handle it.
http://www.gamedev.net/topic/628778-compressing-vertex-attribute-normals/page__p__4965067#entry4965067

People don’t lose respect for you for being wrong. They lose respect for you for handling it poorly.

L. Spiro

I restore Nintendo 64 video-game OST’s into HD! https://www.youtube.com/channel/UCCtX_wedtZ5BoyQBXEhnVZw/playlists?view=1&sort=lad&flow=grid

Paul C Skertich

805

October 11, 2012 03:27 PM

I have been wrong too; it is all about how you handle it.
http://www.gamedev.n...67#entry4965067

People don’t lose respect for you for being wrong. They lose respect for you for handling it poorly.

L. Spiro

True. I probably woke up on the wrong side of the bed today. You're right bro, if a game critic gave me poor game review - probably would aggravate me. So, yeah - I agree I have to react more proactive and professional about. I also have to realize critizism comes in a helping manner and less of a attack. I was being defensive and that's not good demonstration for others to see on this forum. Professionalism is the way to lead people in the right direction. Which, again I have to work upon if I am ever going to be taken seriously. So, yeah I agree with the quote above.