Get Input from the source code itself C++

Question

I want to do something like this

// Example program
#include <iostream>

/*

//IF 
//ASKED FOR INPUT :
//12

*/ 

int main()
{
  int myInt;
  std::cin >> myInt;
  std::cout << myInt;
}

I want this snippet to print 12

I want the code to do something like what the commented part states.

I know I can use standard output and just type it in there. But, my IDE dosen't allow that and I don't want to read it from a file either. Any suggestions?

Before, I thought I can use #defineto redefine the purpose of cin and read from the top of the file instead. But, I'm not sure if it would work or how to implement it either.

*"my IDE dosen't allow that"*. Strange, which IDE do you use? — Jarod42, Aug 05 '18 at 01:37
@Jarod42 It's a custom IDE made by the school. That's why :( — Devansh Sharma, Aug 05 '18 at 01:42
One option is to receive the value as a program parameter. You would need to use `int main(int argc, char **argv) {}` and configure your IDE to pass a parameter when it runs the code (https://stackoverflow.com/questions/3024197/what-does-int-argc-char-argv-mean). — HugoTeixeira, Aug 05 '18 at 01:55

score 1 · Answer 1 · answered Aug 05 '18 at 02:02

1

Maybe stringstream might help:

#include <iostream>
#include <sstream>


int main() {
    std::stringstream ss("42");

    int i;
    ss >> i;
    std::cout << i;
}

Demo

answered Aug 05 '18 at 02:02

Jarod42

203,559
14
181
302

1

You could use a raw string literal so that the OP can just copy and paste the contents of a file into the source code with the line breaks and everything. – eesiraed Aug 05 '18 at 03:30
@FeiXiang Could you explain how to do that? – Devansh Sharma Aug 07 '18 at 23:00
@DevanshSharma: raw string literal is `R"(some_text which may contain quote as " or backslash as \ )"`. – Jarod42 Aug 07 '18 at 23:53

score 0 · Answer 2 · answered Aug 05 '18 at 02:06

You could have two different builds based on a #define value. Use stringstream as an input:

#include <iostream>
#include <sstream>

#define USING_FAKE_STREAM
#ifdef USING_FAKE_STREAM
    std::stringstream g_ss;
    void initStream()
    {
        g_ss << "12\n";
    }

    std::istream& getInputStream()
    {
        return g_ss;
    }
    #else
    void initStream()
    {
    }

    std::istream& getInputStream()
    {
        return std::cin;
    }
#endif

int main()
{
    initStream();

    auto& inputStream = getInputStream();

    inputStream >> myInt;
    std::cout << myInt;

    return 0;
}

Get Input from the source code itself C++

2 Answers2