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Tips and Techniques: Convert Numeric Data in RPG III

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I've written several articles on how to convert numeric data stored in a character field to a true numeric field. But these articles have always referenced RPG IV as the base language--and for good reason: RPG IV is infinitely easier to program in than RPG III could ever hope to be, and RPG IV's expression support does not implicitly convert character data to numeric.

In RPG III and RPG IV, the MOVE opcode implicitly converts data from character to numeric, so there hasn't been much reason to create a routine that would convert numeric data in a character field into a numeric value; just use the MOVE opcode!

But someone recently asked me how to copy numeric data that is stored in a character field along with some garbage characters into a numeric field. Obviously, they want the garbage to be filtered out.

To do this, you need to perform four basic steps.

  1. Figure out what the garbage characters are.
  2. Remove the garbage characters from the original character field.
  3. Right-justify and zero fill the number within the character field.
  4. Copy it to the target packed or zoned decimal field.

Step 1 is so easy to do that it is purely overlooked. To accomplish this, I set up two named constants as follows:

I              '0123456789.-'        C         NUMS
I              '            '        C         BLKS

The NUMS constant contains all the numeric digits and the minus sign. The BLKS constant is all blanks.

These two fields are then used with an XLATE opcode to remove the good data from the original source value.

In the following example, I translate the numeric digits, the decimal notation symbol, and the minus sign (if applicable) to blanks. The MYFLD field is the original character field that contains both the numeric value and the garbage I want to remove. The field named NONNUM is the target of the XLATE. It receives the garbage data, along with a few blanks.

.....C..n01n02n03Factor1+++OpCodFactor2+++ResultLenDXHiLoEq
     C           NUMS:BLKS XLATEMYFLD     NONNUM

Next, the garbage must be removed from the numeric field. There are two ways of doing this, depending on the format of the original data.

If the original data contains an integer (whole number) that also contains some garbage either before or after the value, we use a combination of the CHEKR (check right) and CHECK (check left) opcodes to isolate the numeric data. Then, we use substring to extract the digits, leaving them left-justified in the character field.

If the original data contains thousands notation (i.e., commas) in addition to the garbage, you use a combination of concatenation and CHECK and CHEKR to accomplish a similar task. I have not implemented this option in this example.

Once the numeric digits are isolated inside the character field and are left-justified, you need to right-adjust the data and zero fill it on the left side. This is extremely easy by using a DO loop and the CAT opcode.

The full, working example is illustrated below and is written in RPG III. I first wrote it in RPG IV simply because my RPG III skills are evaporating with time. But I did use short field names and avoided expressions. In fact, if I were to convert this RPG III source to RPG IV, it would look essentially the same as it did when I originally wrote it.

     H
      **  Convert Character to Numeric in RPG III
      **  To use, set the value of FLDLEN equal to
      **  the length of the character variable that
      **  contains your numeric data. In this example,
      **  I use the MYFLD field to store the text form
      **  of the numeric value. I've initialized it also.
      **  Obviously, in a real-world situation, that 
      **  initial value would not be there, but rather 
      **  it would use your runtime value.
     I              '0123456789-'         C         NUMS
     I              '           '         C         BLKS
      ** The following data structure contains all the
      ** work fields I used in this example. In a real-
      ** world situation, these fields may be declared
      ** in a similar data structure but the MYFLD field
      ** would be replaced with the actual name of the 
      ** character field that contains the numeric data, 
      ** and it would not be part of this data structure.
      ** In addition, the target field, NUMVAL in this
      ** example, would also be a standalone field that
      ** was probably declared elsewhere in the code.
     IFIELDS      DS
     I                                    P   1   30STR
     I                                    P   4   60ENDPOS
     I                                    P   7   90LEN
     I                                    P  10  120CNT
     I                                    P  13  170NUMVAL
     I                                       18  37 NONNUM
     I I            '  2345<>(('             38  47 MYFLD
      ** Be sure to initialize this field to the 
      ** length of your original character field.
      ** That is, the character field that contains
      ** the numeric data. In this example, the
      ** MYFLD field is 10 positions, so we initialize 
      ** the FLDLEN field to 10.
     I I            10                    P  48  500FLDLEN
      **
.....C*Rn01n02n03Factor1+++OpCodFactor2+++ResultLenDXHiLoEq
      ** First, convert all the digits to blanks so that
      ** we end up with the NONNUM field containing only
      ** the crap we want to get rid of.
     C           NUMS:BLKS XLATEMYFLD     NONNUM
      ** Next, find the start and end positions of the
      ** real numeric data in the character field.
     C           NONNUM    CHEKRMYFLD     ENDPOS
     C           NONNUM    CHECKMYFLD     STR   
     C           ENDPOS    SUB  STR       LEN
     C                     ADD  1         LEN
      ** Isolate the digits and the sign (if applicable)
      ** from the original character variable. After this
      ** operation, the MYFLD field should contain only
      ** digits and be left-justified.
     C           LEN       SUBSTMYFLD:STR MYFLD     P
      ** Now, check to see how many positions are on the
      ** right side of the digits. 
     C           ' '       CHEKRMYFLD     ENDPOS
      ** Right-adjust and zero fill the numeric value
      ** in the original character field.
     C           FLDLEN    SUB  ENDPOS    CNT
     C                     DO   CNT
     C           '0'       CAT  MYFLD:0   MYFLD
     C                     ENDDO
      ** At this point, the number has been cleaned up and
      ** may be copied to the packed decimal number properly.
     C                     MOVE MYFLD     NUMVAL
      ** ENDPROC;
     C                     MOVE *ON       *INLR

Bob Cozzi has been programming in RPG since 1978. Since then, he has written many articles and several books, including The Modern RPG Language--the most widely used RPG reference manual in the world. Bob is also a very popular speaker at industry events such as RPG World and is the author of his own Web site and of the RPG ToolKit, an add-on library for RPG IV programmers.

BOB COZZI

Bob Cozzi is a programmer/consultant, writer/author, and software developer. His popular RPG xTools add-on subprocedure library for RPG IV is fast becoming a standard with RPG developers. His book The Modern RPG Language has been the most widely used RPG programming book for more than a decade. He, along with others, speaks at and produces the highly popular RPG World conference for RPG programmers.


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