Crosses Initialization in switch case with different size of array per case

Question

void setup()  {
 Serial.begin(9600);
}

void loop()
{
 time_Text(2);
}

void time_Text(int PastTo_val) {
  switch (PastTo_val) {
   case 1:
   {
    int tPTT_y[] = {11, 11, 11, 11};
    int tPTT_x[] = {6, 7, 8, 9};
  }
  break;
case 2:
  {
    int tPTT_y[] = {11, 11};
    int tPTT_x[] = {10, 11};
  }
  break;
 }

 int n_tPTT = sizeof(tPTT_x) / sizeof(tPTT_x[0]);

 Serial.print(tPPT_y);
 Serial.print(" : ");
 Serial.print(tPPT_x);
 Serial.print(" : ");
 Serial.println(n_tPPT); 

}

I have a case that I need to assign different kind of array value (with different size per case), and then find the size of the array, and print it. The problem is that the tPTT_y and tPTT_x is a local variable which cannot be accessed outside of the case function. I have tried to declare it before the switch function but I cannot give a size number because the size is different per case, how could I solve this?

Michel Keijzers · Accepted Answer · 2018-03-26 08:43:22Z

1

Create two global arrays that contain the maximum amount of number you ever need, e.g.

int tPTT_x[4];
int tPTT_y[4];

Than create one global int that contains how much x and y are filled, e.g.

int filled;

Than you can change your cases to

void time_Text(int PastTo_val) {
  switch (PastTo_val) {
   case 1:
   {
    tPTT_y[0] = 11;
    tPTT_y[1] = 11;
    tPTT_y[2] = 11;
    tPTT_y[3] = 11;
    tPTT_x[0] = 6;
    tPTT_x[1] = 7;
    tPTT_x[2] = 8;
    tPTT_x[3] = 9;
    filled = 4;
  }
  break;
case 2:
  {
    tPTT_y[0] = 11;
    tPTT_y[1] = 11;
    tPTT_x[0] = 10;
    tPTT_x[1] = 11;
    filled = 2;
  }
  break;
 }

Than you can use the 'filled' variable to see how many items in the array are 'valid' (0 <= item < filled).

edited Mar 26, 2018 at 8:43

answered Mar 26, 2018 at 8:37

Michel Keijzers

13k7 gold badges43 silver badges59 bronze badges

@MaximilianGerhardt Thanks for the remark (don't have a compiler at hand). I fixed it in my answer.

Michel Keijzers
– Michel Keijzers

2018-03-26 08:43:53 +00:00
Commented Mar 26, 2018 at 8:43

Add a comment |

Maximilian Gerhardt · Accepted Answer · 2018-03-26 16:56:57Z

Just create a buffer of a maximum value and copy in the value you want while remembering the length of the array.

#define MAX_ARR_LENGTH (4)

void time_Text(int PastTo_val) {
    int tPTT_x[MAX_ARR_LENGTH];
    int tPTT_y[MAX_ARR_LENGTH];

    const int tptt_y_case_1[] = {11, 11, 11, 11};
    const int tptt_x_case_1[] = {6, 7, 8, 9};
    const int tptt_y_case_2[] = {11, 11};
    const int tptt_x_case_2[] = {10, 11};

    int filled = 0;

    switch (PastTo_val) {
    case 1:
    {
        memcpy(tPTT_x, tptt_x_case_1, sizeof(tptt_x_case_1));
        memcpy(tPTT_y, tptt_y_case_1, sizeof(tptt_y_case_1));
        filled = 4;
    }
    break;
    case 2:
    {
        memcpy(tPTT_x, tptt_x_case_2, sizeof(tptt_x_case_2));
        memcpy(tPTT_y, tptt_y_case_2, sizeof(tptt_y_case_2));
        filled = 2;
    }
    break;
    }

    Serial.println("Printing array values");
    for(int i=0; i < filled; i++) {
        Serial.println("tPPT_x["+ String(i) +"] = " + String(tPTT_x[i]));
        Serial.println("tPPT_y["+ String(i) +"] = " + String(tPTT_y[i]));
    }
}

Depending on whether you need to modify the memory you can also just point to constant memory and remember the length.

void time_Text(int PastTo_val) {
    const int* tPTT_x;  //Pointers to the values
    const int* tPTT_y;

    //You make also add "static" if you want to reference this
    //data beyond the scope of the function
    const int tptt_y_case_1[] = {11, 11, 11, 11};
    const int tptt_x_case_1[] = {6, 7, 8, 9};
    const int tptt_y_case_2[] = {11, 11};
    const int tptt_x_case_2[] = {10, 11};

    int filled = 0; //number of elements

    switch (PastTo_val) {
    case 1:
    {
        tPTT_x = (const int*) tptt_x_case_1;
        tPTT_y = (const int*) tptt_y_case_1;
        filled = 4;
    }
    break;
    case 2:
    {
        tPTT_x = (const int*) tptt_x_case_2;
        tPTT_y = (const int*) tptt_y_case_2;
        filled = 2;
    }
    break;
    }

    Serial.println("Printing array values");
    for(int i=0; i < filled; i++) {
        Serial.println("tPPT_x["+ String(i) +"] = " + String(tPTT_x[i]));
        Serial.println("tPPT_y["+ String(i) +"] = " + String(tPTT_y[i]));
    }
}

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