eberon array methods

indexOf method is applied to array to search for specified element:

elementIndex := array.indexOf(elementValueToSearch);

indexOf returns the index of the first element of array which value is equal to the value specified as the first argument. Its logic is equivalent to the following code:

elementIndex := 0;
WHILE (elementIndex < LEN(array)) & (array[elementIndex] # elementValueToSearch) DO
    INC(elementIndex)
END;
IF elementIndex = LEN(array) THEN
    elementIndex := -1
END;

That is a lot of code and it cannot be reused in a library (element type can vary). On the other side this operation is used pretty often so it was implemented as Eberon extension.

indexOf can be applied only if elements type can be used in relation operation, i.e. it cannot be applied to array of records or array of arrays.