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When you have a CHAR() data type, no matter how many characters you enter, the variable will be filled on the right, known as right padded, with spaces. To remove these, use RTRIM. This will change the data from a fixed-length CHAR() to a variable length value.

This way, lsTxt will contain either the file listing or any subsequent errors. With bash, it is also possible to perform two redirects:

As usual, we ll add the header and footer to the report by right-clicking an open area inside the report designer and selecting Page Header; repeat the process and select Page Footer. Now, you ll see all three sections (header, body, and footer) added to the report and ready to host report items.

Figure 25-1. The Impress Presentation Wizard guides you through the creation of a new presentation.

Like lists and tuples, option values are simple constructs frequently used as workhorses in F# coding. An option is simply either a value Some(v) or the absence of a value None. For example, options are useful for returning the value of a search where you may or may not have a result. You see in the section Defining Discriminated Unions that the option type is defined in the F# library as follows: type 'T option = | None | Some of 'T The following is a data structure that uses options to represent the (optional) parents of some wellknown characters: > let people = [ ("Adam", None); ("Eve" , None); ("Cain", Some("Adam","Eve")); ("Abel", Some("Adam","Eve")) ];; val people : (string * (string *string) option) list Pattern matching is frequently used to examine option values: > let showParents (name,parents) = match parents with | Some(dad,mum) -> printfn "%s has father %s, mother %s" name dad mum | None -> printfn "%s has no parents!" name;; val showParents : (string * (string * string) option) -> unit > showParents ("Adam",None);; Adam has no parents val it : unit = () The F# library also includes a module Option that contains useful functions for programming with options. Table 3-10 shows some of these. Although it s easy to code them by hand using pattern matching, it can also be useful to learn and rely on the standard definitions. Table 3-10. Some Sample Functions in the Option Module

A business rule performs actions when conditions defined in the Business Rule Composer are true. For example, an action may modify a value in a message. The BizTalk developer creates a condition from facts, which are pieces of information the rules engine can examine. Most often, the rules engine will examine facts from the messages BizTalk directly processes. The orchestration invoking the rules engine directly provides these facts. However, sometimes a rule needs to be based on facts that are not available in the orchestration. The rules engine can retrieve these external facts with a custom fact retriever. In this example, a business rule will schedule a customer s service request only if the customer s address is in the Northwind database. The customer s address may be different each time the orchestration invokes the rules engine. The customer s address is called a short-term fact because the orchestration provides the fact every time it invokes the rules engine. However, instead of opening a new connection to the database each time the orchestration invokes the rules engine, this example reuses the same connection to the Northwind database over and over again. Reusing the database connection makes it a long-term fact. The BizTalk developer must provide long-term facts to the rules engine with the IFactRetriever interface. The custom fact retriever created in this recipe provides the connection to the Northwind database to the rules engine.

Let s look at an extended example combining all the language features covered in detail so far: a simple Scrabble game with Console output (see Listing 6-10). Scrabble is one of my favorite games. I used to play with my family as a kid (back when, for some unknown reason, we thought playing antitelephonebooth would be a cool idea). I played so much I thought I was a hotshot Scrabble player, that is, until I subscribed to the Scrabble Players Newsletter and found out that I was definitely still at the amateur level. I discovered that there are people who know the Official Scrabble Player s Dictionary from front to back by heart and play obscure combinations of letters that only the initiated know are real words. They may not know what they mean, but they sure know their potential for scoring points. Anyway, the game is interesting to us because it involves several arrays, and copious use of string, so, in addition to demonstrating a functioning class, it will provide a review of the last few chapters. We will implement the full game, but implementing the dictionary and the computer player AI are left as exercises for you to try on your own. Also, we will implement this as a console-based game, and players are asked to enter the location of their plays using the hex coordinates. Yes, I know it s geeky. You could also write an interface for this using Windows Forms, another exercise left for you to try as you like. There are a few things to notice about the implementation. The Scrabble game is one class, and we define some helper classes: Player and Tile. Player and Tile are both reference classes as well. You might think that Tile could be a value class. In fact, it s better as a reference class because in the two-dimensional array of played tiles, the unplayed tiles will be null handles. If we were to create a 2D array of value types, there would be no natural null value for an unoccupied space. The basic memory scheme is illustrated in Figure 6-1. We use both lists and arrays. We use arrays for the gameboard, since it never changes size. The bag of tiles and the players racks of tiles are implemented as lists since they may fluctuate in size. You ll see that we copy the list and the arrays into a temporary variable that we use as the play is being formulated. Once the play is final, the changed version is copied back into the original list or array. The former is a deep copy since we re creating a version we can modify. The latter is a shallow copy. The reference is changed to point to the modified object. It s useful to examine this code see the treatment of the variable workingTiles and workingBoard in the PlayerMove function. Another thing to notice about the arrays is that the array of tiles on the board is an array of handles. You ll see that it starts off as an array of null handles, and as tiles are played, the handles are set to actual objects.

In the discussion of the ClickOnce data directory, we avoided talking about security, and for good reason. That s what demos are all about talk about the good stuff, and don t mention anything else. Well, it turns out that a side effect of using the ClickOnce data directory is that you need unrestricted access to the file system. Why Well, you don t know the actual path to the data directory so you can t request FileIOPermission to that folder. Thus, you need unrestricted access to the file system to ensure access to the data directory.5 That s just part of the problem; the other issue deals with using the ClickOnce APIs. As you saw with the sample applications, using the data directory requires that you use the ClickOnce APIs because one of the benefits of the data directory is that you can migrate files from version to version. It turns out that the ClickOnce APIs, for the most part, require full trust if you deploy a partial trust application that attempts to use the ClickOnce APIs, you ll most likely get security exceptions. We say likely because most of the methods (and properties), directly or indirectly, require full trust. You can, however, get by with partial trust for isolated cases. For