5 Quick Tips for C++

In today’s cpp::daily we’re going to talk about commonplace issues that take time searching the internet and often find not-so-good solutions for what we want!

There are 5 tips, but we will probably have other parts!

01. Print the variable type

To know the type of variable just include the header #include <typeinfo> use tydeid( var ).name(), example:

#include <iostream>
#include <typeinfo>

int main(){
  auto a = 12;
  auto b = true;
  auto c = 'M';
  auto d = 3.14;
  std::cout << "Integer: " << typeid(a).name() << '\n';
  std::cout << "Bool: " << typeid(b).name() << '\n';
  std::cout << "Char: " << typeid(c).name() << '\n';
  std::cout << "Double: " << typeid(d).name() << '\n';
  return 0;
}

Remembering that the output will be the initial of the type name, for this example it will be: i of int, d of double and so on. For some other types you will need to filter the output information.

02. Get your screen resolution

We know how to get this via the command line, but to use 100% C++ just include the #include <X11/Xlib.h> lib, in this example for X.org

#include <iostream>
#include <X11/Xlib.h>

int main(){
  Display * d = XOpenDisplay(NULL);
  Screen *  s = DefaultScreenOfDisplay(d);
  std::cout << "Resolution Height: " << s->height << '\n';
  std::cout << "Resolution Width: " << s->width << '\n';
  return 0;
}

Compiling: g++ resolution.cpp -lX11

03. Convert string to char

If you to search in Google this you will see a lot of complex solution worth that Khaby Lame meme.

But this can be done in a very simple way:

std::string str = {"Lorem Ipsum"};
char * chr = &str[0];
std::cout << "The string str now is char: " << chr << '\n';

04. Converting string to integers

Speaking of converting, to convert integer types to string just use the STL itself, this is very useful when we are developing graphics applications. Examples:

#include <iostream>

int main() {
  std::string str = {"30"};
  std::cout << "To int: " << std::stoi( str ) + 6 << '\n';
  std::cout << "To float: " << std::stof( str ) + 1.4f << '\n';
  std::cout << "To double: " << std::stod( str ) + 1.89 << '\n';
  std::cout << "To long int: " << std::stol( str ) * 273 << '\n';
  std::cout << "To long long: " << std::stoll( str ) * 3500 << '\n';
  std::cout << "To long double: " << std::stold( str ) * 189.53254 << '\n';
  return 0;
}

05. Removing whitespace from a string

We know that many programming languages have the functions ltrim()(remove left/start whitespace), rtrim()(remove right/end whitespace) and trim()(remove left/left whitespace/ start and right/end) .

Se nós usarmos aquela solução default do algorithm , provavelmente iremos remover não somente da esquerda e da direita como entre as letras/caracteres também, exemplo:

#include <iostream>
#include <algorithm>

int main(){
  std::string str = " text with blank spaces ";
  str.erase(remove(str.begin(), str.end(), ' '), str.end());
  std::cout << "'" << str << "'" << '\n';
  return 0;
}

Output: 'textwithblankspaces'

So to remove trim() style would be:

#include <iostream>
#include <algorithm>

int main() {
  std::string str = " text with blank spaces ";
  str.erase(str.begin()); //remove at the beginning(left) 
  str.erase(str.end() -  1); //remove at end(right)
  std::cout << "'" << str << "'" << '\n';
  return 0;
}