 Let's say we want to match every number in a text. Numbers are made up of one or more digits concatenated together. Using our basic reject symbols that would be any digit. 0 or 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 concatenated with 0 or more of any digit. 0 or 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 star. Now this is far too long for a busy computer scientist. Thankfully we can use some extended reject syntax to describe this and others using only a few symbols. In many systems a list of symbols between square brackets like bracket 0, 1, 2, 3, 4, 5 bracket means choose one from this list and we can shorten this further to bracket 0-5 bracket which means choose any symbol in the range 0 to 5. But in our example we want any single digit so we can use another code backslash d. Backslash d, backslash d star is so much shorter now but it still matches exactly the same pattern. In fact we can shorten it even more by introducing the plus notation. While a star matches 0 or more a's a plus matches 1 or more a's so we can now write our rejects formula that will match any number as backslash d plus. Other common symbols are the question mark which matches an optional occurrence of the symbol, a number in curly braces which matches exactly that number of the previous symbol and the period or full stop which matches any single character once. Remember all of these extended rejects symbols may be pretty fancy and they shorten things a lot but they are really just shortcuts that could be written longhand using the four basic symbols bar, star and the parentheses.