Built-in functions are becoming common in the world of RPG IV programming, especially since the advent of free-format RPG. BIFs %eof and %found are becoming old friends to us. But have you tried some of the more-complex BIFs? This TechTip will explain one of these, %replace, and perhaps you will give this BIF a place in your next project.
The %replace BIF has been with RPG IV since V4R2, but my guess is that not many programmers routinely use it. It's a highly loaded BIF, meaning that it can perform many different functions. It has four parameters and the following general format:
This BIF returns a character string.
The first function, and most obvious based on its name, is a character replacement in a character-string variable. This BIF is different from the %subst BIF in that neither the from-string nor the to-string parameters are modified as a result of using the %replace BIF. Let's compare %replace and %subst with an example:
D Field2 S 9 Inz('ZYXWVUTSR')
D Answer S 14
Let's assume we want to put four characters from Field2, starting at position 3, into Field1, starting at position 3. The answer needs to go in field Answer, without modifying either Field1 or Field2.
Using %subst:
Answer = Field1;
%subst(Answer:3:4) = %subst(Field2:3:4); // Answer= 'abXWVUghi'
Using %replace:
Answer = %replace(Field2:Field1:3:4); // Answer= 'abXWVUghi'
The example above shows a simple one-to-one replacement, all done in one instruction.
Another useful application of %replace is to emulate the fixed-format Movel operation. The Eval operation can emulate Movel with blank padding, but it doesn't do so well without padding. The %replace BIF can emulate Movel without padding. This will be helpful if you have decided to convert to free-format RPG IV, where Movel is not available. Here's an example:
D TwoChar S 2 Inz('XY')
Let's assume we want to replace the first two characters of Field1 with 'XY', coming from the field TwoChar:
Field1 = %replace(TwoChar:Field1); // Field1 is now 'XYCDEF'
The next function to be illustrated is character-string insertion. To clarify, think of how you insert text into a word document using a PC document editor. The editor inserts text at the desired point as you type. Consider the following example:
D NewChar S 4 Inz('sea')
D Answer S 30
/free
Answer = %replace(NewChar:Text1:11:0);
The 0 for length sets the function to insert text. The field Answer now contains 'She sells sea shells'. Notice that Text1 is too small to contain the result, but Answer is large enough. If by chance Answer is too small to contain the complete new string, trailing characters are truncated without a program exception.
Using the %replace BIF eliminates the need for complex sub-stringing and concatenation expressions.
The last function to be explained is the string-deletion function. Again, think of how you delete characters in a string when using a PC document editor. The editor removes a character at the desired point as you strike the Delete key. Consider the following example:
D Answer S 30
/free
Answer = %replace('':Text1:5:7);
The two consecutive apostrophes in the first parameter tell the BIF to delete. Field Answer now contains 'She sells shells'. Text1 is not modified.
The %replace BIF has no counterpart in CL or original fixed-format RPG operation codes. These marvelous character-string functions can make your data manipulation programming easier to code and maintain. Try it!
Jim Martin, the author of Free-Format RPG IV, is a corporate technical instructor at Jack Henry & Associates in Monett, Missouri. He is a veteran of RPG programming, beginning in 1967 with a position at IBM as a systems engineer and later as a staff programmer at the Rochester systems programming lab. He is a speaker at COMMON and local midrange user group meetings and conferences. For eight years, he was at Lakeview Technology as an AS/400 and RPG instructor. He can be reached by email at
Jim Martin holds a BS degree in mathematics and an MS in computer science. For 26 years, he was employed by IBM, where he wrote RPG applications for customers and worked in the programming laboratory as a programmer on portions of CPF and the OS/400 operating system. After leaving IBM, Jim took post-graduate work in computer science and performed RPG training. He is an IBM-certified RPG IV developer and author of multiple bestselling editions of Free-Format RPG IV, which, since the book's initial publication in 2005, have taught thousands of RPG IV programmers how to be successful with the free-format coding style.
MC Press books written by Jim Martin available now on the MC Press Bookstore.
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