Comparing strings

[deleted account xyzzy]

You can't use C string functions on C++ strings. With C++ strings you compare two strings using the equality operator==.

#include <iostream>
#include <string>

int main()
{
   std::string a;
   std::string b("hello");

   std::cout << "Enter a word to compare: ";
   std::cin >> a;

   if (a == b)
   {
      std::cout << "Equal\n";
   }
   else
   {
      std::cout << "Not equal\n";
   }
}

It's very helpful if you post a Short, Self Contained, Correct (hopefully Compilable), Example (SSCCE). as I did.
http://www.sscce.org/

[deleted account xyzzy]

Another thing to note, there is a newer way to initialize variables, std::string b {"hello"};

This is known as "Uniform Initialization," added in C++11.
https://mbevin.wordpress.com/2012/11/16/uniform-initialization/

There is a very good online and free C++ tutorial you might want to poke around: https://www.learncpp.com/

[seeplus]

You can't use C string functions on C++ strings.

Not directly, but can if you .c_str() with them - although using the specific C++ string operations (or std::algorithm functions) are much the better way as George shows above.

[JLBorges]

> but can if you .c_str() with them

Only if the C++ string does not contain null characters.

#include <iostream>
#include <string>
#include <cstring>

int main()
{
    std::string str = "this is a string" ;
    str[7] = 0 ;
    const char* cstr = str.c_str() ;
    const char* substr = "str" ;

    std::cout << "C++: len == " << str.size() << '\n' // 16
              << "  C: len == " << std::strlen(cstr) << '\n' // 7
              << "C++: " << ( str.find(substr) != str.npos ? "found" : "didn't find" ) << " substring '" << substr << "'\n" // found
              << "  C: " << ( std::strstr(cstr,substr) ? "found" : "didn't find" ) << " substring '" << substr << "'\n" ; // didn't find
}

http://coliru.stacked-crooked.com/a/af0de985bcb49969

[deleted account xyzzy]

And "not directly" is why I said the C functions can't (shouldn't) be used on C++ strings. Using c_str() is not exactly a topic for a beginner just starting out IMO.

[deleted account xyzzy]

wiwbiz wrote:

I am coding in C++ in Dev-C 6.3

Dev-C++ in all its various incarnations have problems, including the recent forks by Embarcadero and Red Panda. The IDE won't allow for any use of C++ language standard beyond C++11 even when the underlying compiler is capable of a later language standard.

If you are able get a newer compiler/IDE, there are free ones available that will allow using a later C++ language standard.

Visual Studio 2019/2022 is considered one of the best for Windows, along with Code::Blocks.
https://visualstudio.microsoft.com/downloads/
https://www.codeblocks.org/

If command-line compiling is needed consider MSYS2.
https://www.msys2.org/

If your OS is not Windows there are versions of Code::Blocks available. MacOS and *nix have pre-compiled binaries available.

Another issue with Dev-C++ that can show up when using it on Windows 10 x64. 32-bit apps can get blocked by the OS. They will not run. Not always, but enough times it becomes a PITA. 64-bit versions of the same code have no problems.

[jonnin]

that seems off as well.
consider:

a += getch(); //string concat works for individual letters

a[i++] seems like it could go out of bounds here.

also you call getch() twice, that seems wrong, and your condition is wrong.
I think what you want is

char c{};
do
{
    c = getch();
    a+= c;
}while (c != '\r' && c!= '\n') //c++ does not understand your conditions, you have to be explicit.   

note that a can have spaces, b cannot due to cin mechanics.
if you want to allow input of spaces or other whitespace, use getline instead of cin.

[lastchance]

#include <iostream>
#include <string>
using namespace std;
int main()
{
   string a, b;
   cout << "Enter a: ";   getline( cin, a );
   cout << "Enter b: ";   getline( cin, b );
   cout << ( a == b ? "Matched" : "Not matched" ) << '\n'; 
}

[deleted account xyzzy]

Two non-standard headers <bits/stdc++h> and <conio.h> Don't use them.

You are using some bastardized Windows I/O (getch), don't use it. Use C++ I/O. std::cin, std::cout.

Using operator[] for string manipulation is decidedly not a good thing to do IMO.

Did you try the code snippet I provided?

I mentioned earlier a free online C++ tutorial you might want to check out: https://www.learncpp.com/

Learning C++ the correct way would be beneficial instead of the mix of C/C++ you are currently having problems with.

Where did you get that code mess?

I don't mean to sound harsh, but this code is not good C++. It looks like some bad C++ rewrite of string handling from C.

[deleted account xyzzy]

I tried it, yes, I tried it. That is why I said it is not good C++ code. IMO sloppy and a royal mess from just reading what was provided and after throwing it into my copy of Dev-C++.

Hint, hint, using the non-standard headers, especially <bits/stdc++h>, won't work with all compilers. Visual Studio, another IDE I have and use, doesn't have that header.

<conio.h> is a Windows only header. Compilers for other OSes, MacOS and *nix, don't have the header. Even if they did the functionality is very specific to Windows.

Well-written C/C++ code should be as platform neutral as possible.

You want to continue writing sub-standard/non-standard code, that is your choice.

Pax, I'm outta here.

[deleted account xyzzy]

wiwbiz wrote:

I don't think a+ or a[i++] are any different, as both are string.

You instantiate your C++ string as being empty.

a[i++] doesn't increase the string's size, it assumes the string is already of the desired size. That is C string logic that will end up writing past the end of the string's memory.

a+= c; concatenates to the end of the C++ string, increasing the string's size with each added character read from the input stream. Still C string logic that is marginally better. Not good C++, though.

Just read your C++ string directly from the input stream either using std::cin::operator>> or std::getline.
https://cplusplus.com/reference/string/string/getline/

[deleted account xyzzy]

Heh, reporting me, wiwbiz, only shows how trollish you are in refusing to accept criticism and advice instead of kissing your ass.

[seeplus]

Well the OP has now gone the way of all things and disappeared...

[deleted account xyzzy]

I could say I am surprised or disappointed.

Well, I could, but I shan't.