Array is empty after one loop for now reason

[MaximDemeulenaere]

Hello there,

For some reason the my array (codeList) is cleared after searching in the main loop

int codeList[] = {10,15,20,25,30};
int item = 10;
void setup() {
  Serial.begin(9600);
  
  for (int i; i < (sizeof(codeList)) / sizeof(int); i++){Serial.println(codeList[i]);}
}

void loop() {
  // show all items in array
  for (int i; i < (sizeof(codeList)) / sizeof(int); i++){Serial.println(codeList[i]);}

  // search  item in array
  bool succes = false;
  for (int i; i < (sizeof(codeList)) / sizeof(int); i++){
    // if item is in list
    if (item == codeList[i]){
      succes = true;
    }
  }
  
  //print succes ore not
  Serial.print("succes: ");
  if (succes){Serial.println("True");}
  else{Serial.println("False");}

  // delay to make promt readble 
  delay(2000);
}

as you will see in the image, in the setup and the first loop it works. but after that he just forgot the array, even if i use const int codeList.

i have no idea why he would do this. so if somane could help i would be greatfull.

Thanks in advance
Maxim D

[gcjr]

@MaximDemeulenaere

for (int i; i

shouldn't i be initialized to 0? (it's not initialized to anything)

[PaulRB]

@MaximDemeulenaere

but after that he just forgot the array, even if i use const int codeList.

No, the array is ok. The search is failing because of the error that @gcjr found. The loop variable i will not automatically default to zero, except by luck. It will begin at some unknown value, which will probably be greater than the size of the array, so the for-loop will not run even once. I worked the first time because of luck, perhaps some previously unused memory was used which contained zero.

[johnwasser]

Set your compiler warnings to "All" in preferences. you would have gotten these handy warnings:

sketch_jul27a.ino:8:12: warning: 'i' is used uninitialized in this function [-Wuninitialized]
   for (int i; i < (sizeof(codeList)) / sizeof(int); i++)
            ^
sketch_jul27a.ino:17:12: warning: 'i' is used uninitialized in this function [-Wuninitialized]
   for (int i; i < (sizeof(codeList)) / sizeof(int); i++)
            ^
sketch_jul27a.ino:24:12: warning: 'i' is used uninitialized in this function [-Wuninitialized]
   for (int i; i < (sizeof(codeList)) / sizeof(int); i++)
            ^

You would have also gotten some warnings about comparing a signed value (int i) with an unsigned value (sizeof). Those are not a problem in your case but to get rid of the warnings, change "int i" to "size_t i". The type 'size_t' is the type that the 'sizeof' operator returns. Probably 'unsigned int'.

[blh64]

A handy little improvement to your code. Change

sizeof(codeList) / sizeof(int)

to

sizeof(codeList) / sizeof(codeList[0])

That way, if you change the type of codeList (like to a long or byte or ????) your code will continue to work, unchanged.

[guix]

You can break; the loop when the item is found so it doesn't check others items for nothing

You could do this way too : xntsRG - Online C++ Compiler & Debugging Tool - Ideone.com