lambda.cpp

#include <algorithm>
#include <iostream>
#include <vector>
/*
syntax:

[ captures ] <tparams>(optional)(c++20) ( params ) specifiers exception attr ->
ret requires(optional)(c++20) { body } [ captures ] ( params ) -> ret { body }
[ captures ] ( params ) { body }
[ captures ] { body }


[ = ] this means passing parameters by value, but they are read only, you need
to use mutable to modify read only

include all parameters
lambda = [](void) { body };

return type is also void
lambda = [](void) -> void {}
*/

template <typename T> void printVec(std::vector<T> values) {
  for (auto value : values)
    std::cout << value << std::endl;
}

void increaser(int &i) { // function:
  i = i + 1;
}

void transformExample() {
  std::vector<int> x = {1, 2, 3};
  std::vector<int> y(x.size(), 0);
  std::vector<int> z(x);
  std::transform(x.begin(), x.end(), y.begin(), [](int a) { return a += 1; });

  std::for_each(z.begin(), z.end(), [&](int a) { return a = a + 1; });

  // std::for_each(z.begin(), z.end(), increaser);

  printVec(y);
  printVec(z);
}

void count_ifExample() {
  std::vector<int> x = {1, 2, 1, 4, 5, 1, 3};
  int ones;

  ones = std::count_if(x.begin(), x.end(), [](int &a) { return a == 1; });
  std::cout << "Total number of ones in the vector is: " << ones << std::endl;

  auto f = [](int &a) { return a == 1; };
  std::count_if(x.begin(), x.end(), f);
  ones = std::count_if(x.begin(), x.end(), [](int &a) { return a == 1; });
  std::cout << "Total number of ones in the vector is: " << ones << std::endl;
}

bool sortFunc(int x, int y) { return (x < y); }

void labmdaExample() {
  std::vector<int> v1;
  for (int n : {1, 8, 5, 6, 3, 4, 0, 9, 7, 2})
    v1.push_back(n);

  // inline
  std::sort(v1.begin(), v1.end(), [](int x, int y) { return (x < y); });

  // outside
  v1.clear();
  for (int n : {1, 8, 5, 6, 3, 4, 0, 9, 7, 2})
    v1.push_back(n);
  auto cmp = [](int x, int y) { return (x < y); };
  std::sort(v1.begin(), v1.end(), cmp);

  // outside as a function
  v1.clear();
  for (int n : {1, 8, 5, 6, 3, 4, 0, 9, 7, 2})
    v1.push_back(n);
  std::sort(v1.begin(), v1.end(), sortFunc);
}

void lambdaPassByValue() {
  int a, b;
  a = 10;
  b = 12;
  std::cout << a << std::endl;

  auto lambda = [=]() mutable { std::cout << ++a << std::endl; };
  lambda();
  std::cout << a << std::endl;
}

void lambdaPassByRef() {
  int a, b;
  a = 10;
  b = 12;
  std::cout << a << std::endl;

  auto lambda = [&]() {
    std::cout << ++a << std::endl;
    b++;
  };
  lambda();
  std::cout << a << std::endl;
}

int main() {
  //     transformExample();
  //  count_ifExample();
  //    lambdaPassByValue();
  lambdaPassByRef();

  //    auto lambda = []() { std::cout << "Code within a lambda expression" <<
  //    std::endl; }; lambda();
}