def compute_line_col(text, size_tab):
    """Computes the line and column in which each letter of text is located."""
    at_what_line = [0] * len(text)
    at_what_col = [0] * len(text)
    line = 1
    col = 1
    for (position, letter) in enumerate(text):
        at_what_line[position] = line
        at_what_col[position] = col
        if letter == "\n":
            line += 1
            col = 1
        if letter == "\t":
            col += size_tab
        else:
            col += 1
    return at_what_line, at_what_col