.NET/ASP.NET/C#/VB.NET PDF Document SDK

5. There are some technical differences in the way tuples and lists work behind the scenes, but you probably won t notice it in any practical way. And tuples don t have methods the way lists do. Don t ask me why.

This time the regular expression matches the two characters that are anchored to the end of any lines within the string.

Note If you want to anchor to the absolute start or end of a string, you can use \A and \Z respectively,

FIGURE 1-3 The images from Mark s PowerPoint presentation filled the 10-foot screen behind him,

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Previously, you used iterators to move through sets of numbers, counting from 1 to 10 for example. What if you want to iterate through a string and have access to each section of it separately scan is the iterator method you require:

"xyz".scan(/./) { |letter| puts letter }

So, you may wonder how to write a tuple containing a single value. This is a bit peculiar you have to include a comma, even though there is only one value: >>> 42 42 >>> 42, (42,) >>> (42,) (42,) The last two examples produce tuples of length one, while the first is not a tuple at all. The comma is crucial. Simply adding parentheses won t help: (42) is exactly the same as 42. One lonely comma, however, can change the value of an expression completely: >>> 3*(40+2) 126 >>> 3*(40+2,) (42, 42, 42)

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matches the regular expression passed to it. In this case, you ve supplied a regular expression that looks for a single character at a time. That s why you get x, y, and z separately in the output. Each letter is fed to the block, assigned to letter, and printed to the screen. Try this more elaborate example:

"This is a test".scan(/../) { |x| puts x }

To tap into the power of Notes Page view, review the slide headline in the top half of the page, position the cursor in the text box in the bottom half of the page, and then write out what you plan to say about this headline, as shown in the magni ed view of the notes area in Figure 6-8. The text you write in the notes area represents what you ll say while the slide is displayed on the screen, normally for a period of less than a minute. If you nd that you have more to say and your narration extends past the limits of the text box, go back to the story template and break up your ideas across more slides.

This time you re scanning for two characters at a time. Easy! Scanning for all characters results in some weird output, though, with all the spaces mixed in. Let s adjust our regular expression to match only letters and digits, like so:

"This is a test".scan(/\w\w/) { |x| puts x }

The tuple function works in pretty much the same way as list: It takes one sequence argument and converts it to a tuple.6 If the argument is already a tuple, it is returned unchanged: >>> tuple([1, 2, 3]) (1, 2, 3) >>> tuple('abc') ('a', 'b', 'c') >>> tuple((1, 2, 3)) (1, 2, 3)

Within regular expressions there are special characters that are denoted with a backslash, and they have special meanings. \w means any alphanumeric character or an underscore. There are many others, as illustrated in Table 3-4.

FIGURE 6-8 A magnified view of the notes area in Notes Page view, displaying an idea being described in

Anchor for the beginning of a line Anchor for the end of a line Anchor for the start of a string Anchor for the end of a string Any character Any letter, digit, or underscore Anything that \w doesn t match Any digit Anything that \D doesn t match (non-digits) Whitespace (spaces, tabs, newlines, and so on) Non-whitespace (any visible character)

Using the knowledge from Table 3-4, you can easily extract numbers from a string: