#include <stdio.h>
#include <stdlib.h>

// call by value - the argument does not change value
//
void assign_00(float val) {
  val = 99;
  return;
}

// call by reference - the argument changes value,
// but the memory location doesn't
//
void assign_01(float* val) {
  *val = 99;
  return;
}

// call by reference for an array: the memory location doesn't change
//
void assign_02(float* val) {
  val[2] = 99;
  return;
}

// call by reference for an array: the memory location doesn't change
//
void assign_03(float* val) {
  val = new float[10];
  val[2] = 99;
  return;
}

// now we are creating a HUGE memory leak
//
void assign_04(float** val) {
  *val = new float[10];
  (*val)[2] = 99.0;
  return;
}

int main(int argc, char** argv) {

  // let's demonstrate that val doesn't change
  //
  float myval = 27.0;
  fprintf(stdout, "00: address: <%p> value: <%f>\n", &myval, myval);
  assign_00(myval);
  fprintf(stdout, "00: address: <%p> value: <%f>\n\n", &myval, myval);

  // let's demonstrate that val changes value using call by reference
  //
  fprintf(stdout, "01: address: <%p> value: <%f>\n", &myval, myval);
  assign_01(&myval);
  fprintf(stdout, "01: address: <%p> value: <%f>\n\n", &myval, myval);

  // let's use an array, and demonstrate that the pointer doesn't change
  // value because of scope issues
  //
  float aval[10]; aval[2] = 27.0;
  fprintf(stdout, "02: address: <%p> value: <%f>\n", aval, aval[2]);
  assign_02(aval);
  fprintf(stdout, "02: address: <%p> value: <%f>\n\n", aval, aval[2]);

  // now, let's try to allocate memory in the function:
  //  even though memory is allocated in the function, that
  //  memory is lost when the function exits, because the value
  //  of its argument is not changed.
  //
  float* aval2 = new float[5];
  aval2[2] = 27.0;
  fprintf(stdout, "03: address: <%p> value: <%f>\n", aval2, aval2[2]);
  assign_03(aval2);
  fprintf(stdout, "03: address: <%p> value: <%f>\n\n", aval2, aval2[2]);

  // to do this right, we need to use a pointer to a pointer
  //
  float* aval3 = new float[10];
  aval3[2] = 27.0;
  fprintf(stdout, "04: address: <%p> value: <%f>\n",
	  aval3, aval3[2]);
  assign_04(&aval3);
  fprintf(stdout, "04: address: <%p> value: <%f>\n",
	  aval3, aval3[2]);
}