Selecting different arrays using a list of pointers

Question

I have different arrays of different sizes, and a list of pointers to the addresses of each array. How do I select each array using the list of pointers, and access it's elements. On Teensy 3.2 board.

int * arr_list[3]; 
const int arr_sizes[3] = {3,4,5}; // array of the array sizes
const int ar1[3] = {12,2,8}; // arrays of different sizes
const int ar2[4] = {41,3,6,47};
const int ar3[5] = {9,32,1,5,7}; 
void map_arrays(){ // list of pointers with the addresses of the 
 // arrays
arr_list[0] = (int*) &ar1; 
arr_list[1] = (int*) &ar2;
arr_list[2] = (int*) &ar3;
}; 
int arr_number = 1; // select array 
int a = arr_sizes[arr_number]; // the size of the selected array
int *b = arr_list[arr_number]; 
int test = 0;
void setup() {
Serial.begin(57600); //serial monitor 
} 
void loop() {
for (int i=0; i<a; i++) { // for the selected arr_number iterate and
test = b[i]; // return the index elements 
}
Serial.println("size ="); 
Serial.println(a);
Serial.println();
delay(1000);
Serial.println("index ="); 
Serial.println(test);
Serial.println();
delay(500);
 }

• Ignacio Vazquez-Abrams: You terminate each array appropriately.

Answer 1

You have it right, only fix initialization of test variables:

1. you do not call map_arrays() in setup()
2. you assign uninitialized arr_list item to b

const int* arr_list[3];
const int arr_sizes[3] = { 3, 4, 5 }; // array of the array sizes
const int ar1[3] = { 12, 2, 8 }; // arrays of different sizes
const int ar2[4] = { 41, 3, 6, 47 };
const int ar3[5] = { 9, 32, 1, 5, 7 };
void map_arrays() { // list of pointers with the addresses of the
// arrays
 arr_list[0] = ar1;
 arr_list[1] = ar2;
 arr_list[2] = ar3;
}
int arr_number = 1; // select array
int a = arr_sizes[arr_number]; // the size of the selected array
const int *b;
int test = 0;
void setup() {
 Serial.begin(57600); //serial monitor
 map_arrays();
 b = arr_list[arr_number];
 for (int i = 0; i < a; i++) { // for the selected arr_number iterate and
 test = b[i]; // return the index elements
 Serial.println(test);
 }
 Serial.println("size =");
 Serial.println(a);
 Serial.println();
 delay(1000);
 Serial.println("index =");
 Serial.println(test);
 Serial.println();
 delay(500);
}
void loop() {
}