i am trying to compare the elements of two arrays before the code goes on to the next sequence. The elements of note[x] are filled with the note values of a song. and i want to be able to input values from a midi controller into learn[x]. how can i compare array learn[ ] to array note[ ] before the showsequence(); is incremented?

 const int x = 100;
    int note[x];
    int learn[x];
    int largestindex = 0;
    int learnindex=0;
    void showsequence();
    void readsequnce();
    const int PLAY = 1;
    const int TRYAGIN = 2;
    int state=0;

 void loop() {
     if (state == PLAY) {
      else if (state == TRYAGIN) {
    void MyHandleNoteOn(byte channel, byte pitch, byte velocity) {

 void showsequence() {
      //Add a new index to the end of the songseq
      //loop through the songseq
      for (int index = 0; index < largestindex; index++) {

      void readsequnce() {
      static uint16_t nextkey;
      bool mademistake = false;

       if (array_cmp(learn, note, largestindex, largestindex) == true){
               // do this if they are equal
               lcd.setCursor(16, 2);
               // do this if they are different
               lcd.setCursor(16, 2);

 boolean array_cmp(int *a, int *b, int len_a, int len_b){
         int n;

         // if their lengths are different, return false
         if (len_a != len_b) return false;

         // test each element to be the same. if not, return false
         for (n=0;n<len_a;n++) if (a[n]!=b[n]) return false;

         //ok, if we have not returned yet, they are equal :)
         return true;

2 Answers 2


It depends what sort of comparison you want to do. If you want to see if note[x] == learn[x] then that's what you do.

If you want to see if all the notes match all of learn then you'll need to put the comparison in a loop.

for (int n = 0; n < MAX_NOTE && note[n] == learn[n]; ++n)
    // Empty loop

If you want to see if the first n notes match the current note and the proceeding n notes then its a bit more complex, but its just a loop.

int n = 0;
for (int l = currentPos;
(l > (currentPos - 10)) && (note[n] == learn[l]);
 l--, n++)
    // Empty loop

If it is something else you want, please can you try and describe it in idiot proof terms so I can understand it.

  • i want to compare note[x] == learn[x] but then once the compare is matches to compare note[x] == learn[x] (x going from 0->1) increasing by 1 every time the match is correct
    – Hjhk90
    Apr 25, 2017 at 13:41
  • Then use the bottom example, but int n = x, int l = x and l++. You will have to be careful about n and l exceeding the maximum index of the array/data, so add two extra conditions into the third line && n < maxData && l < maxData (Need to set maxData to something sensible. Apr 26, 2017 at 7:07

Start by assuming they match. Loop over each element pair, compare them, and set a flag when you find a pair that don't match.

bool they_match = true; // assume they match 
for ( int i = 0; i < x; i++ ) { // for each note/learn element
  if ( note[i] != learn[i] ) { // check if they don't match
    they_match = false; // they don't mach, so set flag
    break; // stop looping 

At the end they_match will be true if note[] and learn[] match, or false if they don't.

I would suggest you learn how control structures work. https://www.cs.fsu.edu/~myers/c++/notes/control1.html https://www.cs.fsu.edu/~myers/c++/notes/control2.html

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