Thread: struct + vector = fun

I am trying to push individual characters from a string to the back of a vector of structs.. i'm just not sure of the correct syntax to properly pushback to the correct struct attribute.

Code:

#include<iostream>
#include<string>
#include<vector>
#include<conio.h>
using namespace std;


struct letter
{
	char character;
};


int main()
{
	clrscr();

	vector<letter> *nodes;

	string hello = "Hello World";

	for(int i=0; i<12; i++)

		nodes->character.pushback(hello[i]);

	for(int j=0; j<nodes->size(); j++)

		cout << *nodes[j]->character;

	return 0;
}

compiler errors thus far:

Borland C++ 5.5.1 for Win32 Copyright (c) 1993, 2000 Borland
contest.cpp:
Error E2316 contest.cpp 26: 'character' is not a member of 'vector<letter,allocator<letter> >' in fu
nction main()
Warning W8012 contest.cpp 28: Comparing signed and unsigned values in function main()
Error E2288 contest.cpp 30: Pointer to structure required on left side of -> or ->* in function main
()
*** 2 errors in Compile ***


thanks in advance

Code:

#include<iostream>
#include<string>
#include<vector>

using namespace std;

struct letter
{
  char character;
  letter(char init = 0): character(init) {}
};

int main()
{
  vector<letter> nodes;
  string hello = "Hello World";

  for(int i=0; i<hello.length(); i++)
    nodes.push_back(letter(hello[i]));

  for(int j=0; j<nodes.size(); j++)
    cout << nodes[j].character;

  return 0;
}

What was wrong? Let's take a look:

>clrscr();
Silly and nonportable, but I'll ignore it this time.

>vector<letter> *nodes;
Note that this is a pointer to a vector. If you really want a pointer to a vector then you need to use new to actually create it. If you want a vector of pointers to letter then this is the correct declaration:

Code:

vector<letter *> nodes;

Of course, that complicates your usage without any obvious benefit for this program, so I just changed it to a vector of letters.

>for(int i=0; i<12; i++)
std::strings need not be null terminated, you're walking past the end with this loop. 11 would be correct, and hello.length() would be much better.

>nodes->character.pushback(hello[i]);
This is all kinds of wrong. nodes is a pointer to a vector, so the arrow operator is correct (assuming it points to something valid), but character isn't a member of nodes, it's a member of letter. Without an appropriate constructor defined, you would need to do this:

Code:

nodes->push_back(letter());
nodes->back().character = hello[i];

So defining a default and single argument constructor makes a lot of sense.

>cout << *nodes[j]->character;
Operator precedence is a pain. Remember that if you want indirection before indexing, surround the indirection in parens:

Code:

cout << (*nodes)[j]->character;