Prototypes and /COPYs

One of the biggest advantages of using the /COPY statement is that it allows you to import prototypes for procedures. Since most new code written in RPG IV will probably take advantage of procedures and every procedure requires a prototype, the benefit of /COPY and /INCLUDE should become obvious.

Let's assume we have several procedures that we've created for an application. Most of those procedures are written in RPG IV, and some are written in another language, such as C. It turns out that we want to use some of these procedures in multiple applications. For example, we have several "date and time" procedures and perhaps some CGI procedures.

In order to use these procedures, the prototype for the procedure needs to be included in each source member that refers to the procedure--that is, in source members where the procedure is called and in the source member that defines the procedure itself.
So if we have three source members that contain the procedure definitions for several procedures, and those source members are named DATERTN, STRRTN, and SYSTOOLS, we would have something like the following:

When these source members are compiled, an individual *MODULE object is created that contains the compiled code for the procedure. We can then bind by copy (physically bind or copy these modules into our application) or bind by reference (create a service program containing these modules).

In order to call and then bind to any of these procedures, we need to include their prototypes in the source member that contains the call to the procedure. So we create a second set of source members that contains only the prototypes for the procedures, and we end up with something like the following:

These source members will be /COPYed into the source member that contains the call to the procedure. For example, if we need to call the GetEndOfMonth() procedure, we need to include the prototype for that procedure. We can physically code the prototype (bad idea!), or we can simply include the DATES source member by using a /COPY or /INCLUDE directive.

Let's use the GetEndOfMonth procedure as an example. Figure 1 shows the source for the GetEndOfMonth procedure:

Figure 1: This is the source for the GetEndOfMonth procedure example.

Lines 2 and 3 of the GetEndOfMonth procedure contain the procedure interface (the parameter list) for the procedure. The prototype for this procedure would be as shown in Figure 2:

Figure 2: This is the prototype for the GetEndOfMonth procedure example.

The difference between the procedure interface (lines 2 and 3 of Figure 1) and the prototype (line 1 of Figure 2) is that the letters "PI" appear in the procedure definition in positions 24 and 25 of line 2 in Figure 1, whereas the letters "PR" appear in the prototype in the same positions of line 1 in Figure 2. The letters "PR" indicate that the source is a prototype.

A prototype can be included even if its procedure is not called by the source in which it is included. Essentially, prototypes simply help the compiler syntax check the call to the procedure. If the procedure isn't called, its prototype isn't used, so there's no wasted overhead associated with including procedure prototypes you don't use.

You could simply hard code the prototype in the same source member that the procedure is defined in, but then when you need to call the GetEndOfMonth procedure, you'd have to physically copy the prototype into each source member that needed it, and what fun is that?

Using the /COPY or /INCLUDE statements, however, you can simply store the prototype and other related prototypes in a separate source member and then /COPY it into the source that needs it.

For example, suppose an application needs to read a Customer master file and, using a payment due date, calculate a new due date based on a grace period that extends through the end of the month. Then, a report needs to be printed with the customer number and the revised due date.

Figure 3 shows the source for this example application.

Figure 3: Here's an example of where to use the /COPY statement.

The /COPY statement on line 4 of Figure 3 illustrates the ease of including another source member. That's all there is to it. Nothing else needs to be done. When the compiler processes the /COPY statement, the source in Figure 5 is produced.

Figure 5: Here, the /COPY source is expanded.

Note that the prototype (actually, all the source from the included member) is copied into the main source member exactly where the /COPY statement was specified.

Syntax of /COPY and /INCLUDE

The syntax is the same for both /COPY and /INCLUDE, and they can include either regular OS/400 source file members or text files stored in the Integrated File System (IFS). The syntax to include regular OS/400 source members is as follows:

The library name and source file name are optional, but the member name is required. In addition, the /COPY and /INCLUDE statement must have one and only one space between the directive itself and the member name. Here are a few examples:

All three of these /COPY statements are effectively the same. If the library name is not specified, the library list is searched. If the source file name appears in a library name that is high on the library list and it does not contain the member name, the search continues to the next source file on the library list and then the next until the member name is located. The library name (if specified) must be qualified to the source file name, using the forward slash, as in the traditional libname/srcf syntax. If the source file name is not specified, QRPGLESRC is used as the default name, and the library name may not be specified. Any name is valid as long as it is a valid source file object. If the source file name is specified, it is qualified to the member name using a comma, as in the srcf,mbrnam syntax. The member name is always required. The syntax to include source from the IFS is as follows:

When using the IFS file system naming, both the IFS and the so-called QSYS file system can be included. That is, in addition to text files stored on the IFS, regular OS/400 source file members may be included using the IFS naming convention.

The first /COPY includes the text file named DATES.RPG located in the "/cozzi/rpg source" folder of the IFS. Note the embedded blank. When the directory includes an embedded blank, the entire directory and file name must be enclosed in quotes (single or double). When no blanks are embedded, quotes are optional.

The second /COPY statement also includes the dates.rpg file, but it avoids specifying the suffix. If no suffix is specified, the compiler looks for the file without the suffix, and if it does not find it, it looks for the file with a suffix of .rpg. If it cannot find that, it looks for the file with a .rpginc suffix.

The third /COPY statement is the same as the second example, except the quotes are not specified.

The fourth /COPY statement illustrates how the IFS syntax can be used to include regular OS/400 source file members. By starting the IFS directory name with /QSYS.LIB, the so-called "QSYS File system" is searched for the file name.

Start using /COPY or /INCLUDE today! Your code will be happier, and it will create less maintenance issues than you currently have by allowing you to modify prototypes, algorithms, or data variables in one place and then simply recompile.