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RPG IV

RPG IV. Advanced Data Definition and Manipulation- Chapter 11. Objectives. Perform date arithmetic Define data that facilitate data manipulation, error trapping, debugging and program maintenance Use RPG IV built-in functions(BIF’s) to manipulate data. Data Types and Time.

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RPG IV

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  1. RPG IV Advanced Data Definition and Manipulation- Chapter 11

  2. Objectives • Perform date arithmetic • Define data that facilitate data manipulation, error trapping, debugging and program maintenance • Use RPG IV built-in functions(BIF’s) to manipulate data

  3. Data Types and Time • Three data types exist for dealing with time: • Date(D) -10 byte display yyyy-mm-dd • Time(T)- 8 byte display hh.mm.ss • Timestamp(Z) - 26 byte default display yyyy-mm-dd-hh.mm.ss.mmmmmm • Date supports 8 different formats • Time supports 5 different formats • Different separators are supported

  4. Date and Time Operations • ADDDUR, SUBDUR and EXTRCT • Duration codes: • *YEARS (or *Y) • *MONTHS (or *M) • *DAYS (or *D) • *HOURS (or*H) • *MINUTES (or *MN) • *SECONDS (or *S) • *MSECONDS (or *MS)

  5. ADDDUR(Add Duration) • Add a duration coded in Factor 2 to the date specified in Factor 1 • Storing the answer in the date, time or timestamp field specified as the Result field • Factor 2 must contain an integer field or literal

  6. SUBDUR(Subtract Duration) • Has two uses: • Subtract a date/time duration from a date/time value (similar to ADDDUR) • Calculate the duration between two date/time values

  7. Subtract a Date/Time Duration • Subtract a duration coded in Factor 2 to the date specified in Factor 1 • Storing the answer in the date, time or timestamp field specified as the Result field • Factor 2 must contain an integer field or literal

  8. Calculate a Duration Between Two Date/Time Values • Factor 1 and Factor 2 must contain data items of compatible types • Place an integer receiveing field followed by a duration code in the Result field

  9. EXTRCT(Extract Date/Time/Timestamp) • Extract a portion of a data/time or timestamp and store in the Result field • Factor 2 date/time data item must be coupled with a duration code to signal which portion of the data/time unit is to be extracted

  10. Pointer Data Types • Two kinds of pointer data types: basing pointers and procedure pointers • Used to access storage that is allocated dynamically throughout the program • Pointers store address of memory locations rather than data values • Procedure pointers must include the keyword PROCPTR

  11. LIKE (Field Definition) • The keyword LIKE allows you to define a field based on the attributes of another field • The entered number signals the extent of the increase or decrease in field length

  12. Data Structures • Subdivide fields into subfields • Restructure records with different field layouts • Change field data types • Add a second dimension to arrays

  13. Data Structures cont. • DS coded in 24-25 on D spec signals the beginning of a data structure • Enter name of data structure in 7-21 • Follows same rules as field • Use absolute notation or length notation for subfields

  14. OVERLAY • OVERLAY keyword indicates that a subfield overlays the storage of another subfield • If the data time within parentheses is an array, OVERLAY applies to each element of the array

  15. Externally Described Data Structures • Externally described data structures are useful when you want to standardize a data structure • Code an E in position 22 • Name the external file using the EXTNAME keyword

  16. Multiple-Occurrence Data Structures • Repeated data structures • Keyword OCCURS • Number determines how many times the structure is repeated in storage

  17. OCCUR (Set/Get Occurrence of a Data Structure) • OCCUR operation is used to establish which occurrence of the data structure is used next within the program • Factor 1 specifies which occurrence should be made current • Factor 2 contains the name of the DS

  18. Initialization and Reinitialization of Variables • INZ keyword will initialize to default value of data type • *INZSR is a subroutine that will be invoked automatically after the program completes its other start up tasks • CLEAR and RESET will allow you to reinitialize variables

  19. File-Information Data Structures • A special data structure that can be defined for each file used by your program • This data structure contains subfields that provide info to your program about the file and I/O operations • The required entries in the F spec are; keyword INFDS and a parameter with the name of the data structure defined in the D Spec

  20. Program-Status Data Structures • A data structure that can provide you with information about the program itself and about exceptions/errors that occur during program execution • An S in position 23 of a data structure definition line identifies a program-status data structure

  21. Error Handling • Without explicit error handling within your program, any runtime error will cause the system to suspend the program • One technique to code the (E) error-handling extender with those operations that permit such an entry • Then perform an error routine if the %ERROR bif is on

  22. *PSSR • Another error handling technique is to use a special subroutine called *PSSR • This subroutine will automatically receive control when a program error occurs • To send control to this subroutine for file errors, you must explicitly designate *PSSR as the error handler for the file

  23. Field Inspection • %SIZE(Get Size in Bytes) • %LEN(Get or Set Length) • %DECPOS(Get Number of Dec Positions) • %ELEM(Get Number of Elements) • TESTN(Test Numeric) • TEST(Test Date/Time/Timestamp) • SCAN(Scan String) • %SCAN(Scan for Characters) • CHECK(Check Characters) • CHECKR(Check Reverse)

  24. %SIZE • Returns number of bytes or length of string • Used to determine size of field, literal, named constant, data structure, subfield, array or table • One required parameter to represnet data whose size you want to know • Second parameter *ALL- size of entire table, array or data structure

  25. %LEN • Returns number of digits or characters in an expression • Especially useful with character expressions • For numeric expressions %LEN returns the precision of the expression

  26. %DECPOS • Returns the number of decimal positions in a numeric variable or expression • Sometimes used with the %LEN function

  27. %ELEM • Returns the number of elements in an array or a table or the number of occurrences in a multiple-occurrence data structure • Can be used in calculations or when defining other fields

  28. TESTN • Determine whether a character field contains all numeric characters, leading blanks followed by all numeric characters, or all blanks • Used to validate fields before performing calculations

  29. TEST • Checks validity of date, time or timestamp fields • Checks character and numeric fields for valid date/time data

  30. SCAN • Look for a characer or string of character within a character field • Case sensitive - recognizes upper and lower case • Blanks are not ignored

  31. %SCAN • Nearly identical to SCAN • Performs the scan within an expression

  32. CHECK • Similar to SCAN • Checks for discrepancies between individual characters of compare field and base string and signals absence of a base character from set of compare characters and stores it’s location in the result field • Checks left to right

  33. CHECKR • Works exactly like CHECK • Checks the base string from right to left

  34. Field Character Manipulation • + (Concatenate Character Strings) • %TRIM, %TRIML, and %TRIMR (Trim Blanks) • %SUBST(Get Substring) • %DEC(Convert to Packed Decimal Format) • XLATE (Translate)

  35. Concatenate Character Strings • Using the + operator with EVAL is a convenient way to concatenate two (or more) strings to form a new string

  36. Trim Blanks • Remove leading and/or trailing blanks from their argument • %TRIML – removes leading blanks • %TRIMR – removes trailing blanks • %TRIM – removes both leading and trailing blanks

  37. %SUBST • Extracts a portion of a character string • Argument parameters in order: string from which extraction is to occur, position within that string where substring is to start and optional length of substring, parameters separated by a colon

  38. %DEC • Converts the result of the expression to a packed-decimal format • %DECH (Convert to Packed Decimal Format with Half Adjust) • %INT (Convert to Integer Format) • %UNS(Convert to Unsigned Format) • %INTH and %UNSH are half adjust built in functions

  39. XLATE • Translate or convert characters within a string to other characters

  40. Points to Remember • Fields can be defined relative to other field definitions using the keyword LIKE • You can define data structures that represent complex definitions of a given area of memory

  41. Points to Remember cont. • Data structures or subfields of data structures can be initialized easily as part of the data structure definition • Two special data structures of predefined subfields exist in RPG to provide information about the status of files used by the program or about the processing of the program itself

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