not seeing the error

technologist (607)
Trying to pass a pointer to a string via a function. Get the error (at bottom).

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#include<iostream>
#include<string>

using namespace std;

void PrintString( string * string_h)
{
	        cout<<string_h[2];
}

int main()
{

		string * x = 'red';
		PrintString(x);
		return 0;
}


..\src\main.cpp:14:16: error: invalid conversion from 'int' to 'std::string* {aka std::basic_string<char>*}' [-fpermissive]
closed account (48bpfSEw)
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#include<iostream>
#include<string>

using namespace std;

void PrintString( string * string_h)
{
	        cout << string_h->c_str();
}

int main()
{    
		string *x = new string("red");
		PrintString(x);
		delete x;
			
		return 0;
}
TheIdeasMan (6847)
Hi,

Pass the string by const reference:

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void PrintString( const std::string&  string_h)
{
	        std::cout << string_h[2];
}


Try to avoid raw pointers with modern C++.

@Necip
No need to use new and delete, STL containers implicitly store their data on the heap. delete can cause problems: if an exception is thrown, delete is never reached, neither is the destructor.
technologist (607)
Ok, got rid of the namespace (hard habit to break for me sometimes), added some further examples to facilitate my understanding. Sort of mystified that sometimes a ' will trigger an error where a " reconciles it, and sometimes the opposite occurs. For me it has been trial and error in these limited cases.

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#include<iostream>
#include<string>



void PrintString(const std::string &string_h)
{
	std::cout<<"Index [3] of long sentence ="<<string_h[3];
	std::cout<<std::endl;
	char d = 't';
	int index = string_h.find(d);
	std::cout<<"character "<<d<<" found at index "<<index<<" of: "<<string_h<<std::endl;
	std::cout<<"Non-symbolic (magical number)"<<std::endl;
	index = string_h.find('s');
	std::cout<<"character "<<'s'<<" found at index "<<index<<" of: "<<string_h<<std::endl;
}

int main()
{
		std::string string_h;
		string_h= "red";
		char d = 'r';
		int index = string_h.find(d);
		std::cout<<"character "<<d<<" found at index "<<index<<" of: "<<string_h<<std::endl;
		std::cout<<"To function:"<<std::endl;
		string_h = "long sentence";
		PrintString(string_h);

		return 0;
}


Sorry about the excessive tabbing I cannot as of now find the place on my ide where I can change it. (Eclipse)
Last edited on
TheIdeasMan (6847)
Sort of mystified that sometimes a ' will trigger an error where a " reconciles it, and sometimes the opposite occurs.


' ' is for a solitary char, while " " is for strings:

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char a = 'X';
std::string b = "Fred';

although with an array of char " " is used :

char[] c = "Ginger"

But one should avoid char arrays, unless it is required by some library function.

Also, be aware that lots of library functions return a std::size_t type as opposed to int For example std::string::find
technologist (607)
Thank you very helpful. I was going crazy with the ' vs. "
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