mql4 function with array: error parameter conversion not allowed

External question — Stack Overflow Stack Exchange Author: user310291 Original post: https://stackoverflow.com/questions/76200381 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. I created this function and put it above init() but got error parameter conversion not allowed, I don't understand why : int BelongsToArray(int value, int[] array) { int arrSize = ArraySize(array); for(int i=0; i<arrSize; i++) { if(value == array[i]) { return true; // value belongs to array } } return false; // value does not belong to array }

External answer — Stack Overflow Stack Exchange Author: Jalal Nouri Original post: https://stackoverflow.com/a/76205105 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. This function only accepts integer type array, but in the body of your code, you must have given it an array that is not an integer type (such as double ) as input. So, to find the cause of the error, refer to the places in your code where you have called this function (that is, BelongsToArray ). Also in the function argument part, the second input, the array must be passed by reference. Therefore, it should be corrected as follows: int BelongsToArray(int value, int &array[]) I have a suggestion. Because the output of the function is boolean, it is better to use bool instead of int in the header of the function. However, if this is not done, the code will still work correctly.