CODEWITHSUNDEEP
arduinoarduino-ide
proto
proto

Reputation: 5

Arduino - For Loop with Array not working

I have a problem with for loops and an array in Arduino IDE.

How can I get test1 to work?

void test1(){
    for(int i=1; i<5; i++) {
    individualPixels[i]==1;
  }
}
void test2(){
    individualPixels[1]=1;
    individualPixels[2]=1;
    individualPixels[3]=1;
    individualPixels[4]=1;
  }
}
void test3(){
    for(int i=1; i<5; i++) {
    Serial.println(individualPixels[i]); //prints out 0 4 times
  }
}

Upvotes: 0

Views: 4935

Answers (4)

proto
proto

Reputation: 5

Thanks very much to all of you. I have a large array with 60 indexes and want to set some of them 1 with a for loop. The "==" was the main problem. It's working now like I want it to:

void test1(){
    for(int i=1; i<5; i++) {
    individualPixels[i]=1;
  }
}
void test2(){
    individualPixels[1]=1;
    individualPixels[2]=1;
    individualPixels[3]=1;
    individualPixels[4]=1;
}
void test3(){
    for(int i=1; i<5; i++) {
    Serial.println(individualPixels[i]); //prints out 0 4 times
  }
}

Upvotes: 0

Alexander Bollaert
Alexander Bollaert

Reputation: 804

You're not actually assigning anything in test1, you're testing for equality (individualPixels[i]==1 should be individualPixels[i] = 1, note the single equality sign).

Also, as other commenters mentioned, C/C++ uses zero based indexing.

Upvotes: 1

Lucurious
Lucurious

Reputation: 174

The for loops start with i = 1 that should be 0 as an element in an array can be accessed with an index from 0 to size-1. An array with 4 elements can be accessed as follows:

array[0] --- first element
array[1] --- second element
array[2] --- third element
array[3] --- fourth element

Apart from that, the first for loop (that doesn't work) used the == operator, which checks if two variables are equal and then returns a boolean as a result. Instead you should use a single = that will set the value.

The second test has an extra } ,which should be removed

I suggest you to start actually learning programming, for example by reading a (e)book, as you will teach yourself bad habits (accessing arrays in a wrong way), which may work, but may not be efficient.

Upvotes: 1

imjosh
imjosh

Reputation: 4872

C/C++ uses zero indexed arrays, so your for loops in test1 and test3 should look like this:

for(int i=0; i<4; i++) {
    individualPixels[i]==1;
}

Test2 has an unmatched bracket and the array indexes should start at zero:

void test2(){
    individualPixels[0]=1;
    individualPixels[1]=1;
    individualPixels[2]=1;
    individualPixels[3]=1;
  //} this shouldn't be here
}

Upvotes: 1

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