#include <Foundation/Foundation.h>

typedef id (^Function)(id);

// a commodity for "encapsulating" double f(double)
typedef double (*func_t)(double);
Function encapsulate(func_t f) {
  return ^(id x) { return @(f([x doubleValue])); };
}

Function compose(Function a, Function b) {
  return ^(id x) { return a(b(x)); };
}

// functions outside...
double my_f(double x)
{
  return x+1.0;
}

double my_g(double x)
{
  return x*x;
}


int main()
{
  @autoreleasepool {

    Function f = encapsulate(my_f);
    Function g = encapsulate(my_g);

    Function composed = compose(f, g);

    printf("g(2.0) = %lf\n", [g(@2.0) doubleValue]);
    printf("f(2.0) = %lf\n", [f(@2.0) doubleValue]);
    printf("f(g(2.0)) = %lf\n", [composed(@2.0) doubleValue]);

  }
  return 0;
}