Need to access an element from part of a string array

Question

Suppose I have this code:

#include <iostream>
#include <string>

using namespace std;

int main()
{
    string disectedString[5];

    disectedString[0] = "011001";

    string temp = disectedString[0];
    string print = temp[0];

    return 0;
}

So I'm selecting an element out of my array of strings, and then assigning it to a temp variable. From there, I want to select the first element out of the temp variable,(the first character). How would I go about doing this?

Have you considered reading [the documentation](https://en.cppreference.com/w/cpp/string/basic_string)? — Useless, Jul 13 '18 at 14:35
`temp` is a `std::string`. Elements of `std::string` are `char`, not another `std::string`. — François Andrieux, Jul 13 '18 at 14:37
I'd suggest you start by reading [a good book](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). Trial and error is not a good method for learning C++ :) — Yksisarvinen, Jul 13 '18 at 14:38
Other than using the wrong type for `print` your program does do what you wanted to. — einpoklum, Jul 13 '18 at 15:04

einpoklum · Answer 1 · 2018-07-13T15:50:45.760

Your intuition is mostly valid: You use the square brackets operator, [], to access the element at an indexed position within a collection or sequence. Thus

disectedString[0] means "the first element of disectedString";
temp[0] means "the first element of temp";

What you've gotten mixed up are the types, as commenters and @demogorgon.net's answer have explained.

Now, with modern C++ you can "play dumb" and not declare what you know the types to be:

std::string disectedString[5];
disectedString[0] = "011001";
auto temp = disectedString[0];
auto print = temp[0];

Note the use of auto instead of a specific type name. This will work as you would like it to. You can then use use print, and do, for example:

std::cout << print;

and this will output 0.

By the way, I believe you should reconsider your choice of names:

Intuitively, print should refer to a function, or a method, which prints things; I'd suggest first_character or char_to_print or just c if you want to be brief.
temp is no more a temporary variable than, say, print.
It's better to avoid variable names which contain the type name, although we sometimes sort of have to resort to that. Specifically you using the word 'string' in variable names; probably not a good idea.
Your disectedString variable is not a string, it's an array of strings, which is confusing.

demogorgon · Answer 2 · 2018-07-13T15:09:38.370

1

A string behaves in many ways like an array of char's (*). You need to set print to char type instead of string since you are trying to get a specific element from the string. So your print should look like this:

char print = temp[0];

_{(*) but it's really more complicated than that.}

Here is a code example that prints the output.

edited Jul 13 '18 at 15:09

answered Jul 13 '18 at 14:52

demogorgon

474
4
20

1

I wouldn't really say `std::string`s are essentially arrays of `char`s. They behave like them to some extent. – einpoklum Jul 13 '18 at 14:58
@einpoklum yes that's correct. I only say essentially because on the most basic level, this is easy to comprehend for someone learning c++. but you are right :) – demogorgon Jul 13 '18 at 14:59
Also, why do you insist OP used `temp.at()` instead of `temp[0]`? The latter is [perfectly valid code](https://en.cppreference.com/w/cpp/string/basic_string/operator_at). – einpoklum Jul 13 '18 at 15:03
ughh you are right, idk why to be honest, especially after I just said its like an array of `chars`. editing it now. @einpoklum – demogorgon Jul 13 '18 at 15:07

Need to access an element from part of a string array

2 Answers2