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Re: Reasons for using RPGIV



fixed

Please feel free to correct anything I may have gotten wrong or need to
reword to make more understandable...
- sjl


I wrote:
Here is what I have come up with so far - see below...
- sjl


RPGIV versus RPG/400 (V5R4M0)
April 14, 2011


Subprocedures and prototypes

o Code isolation

* local variables

* Simplifies program changes and testing

* Lowers coupling between modules (a good thing)

o Simplifies program coding when using service programs (which contain
reusable subprocedures)

* Enhances productivity though code re-use

o Binding source makes it possible to add new subprocedures
to existing service programs without having to
recompile all programs which use the service program.

* Mixed programming language support by allowing modules
written in different ILE languages to be bound into a
single program object

* Performance improvement when using bound programs

o Prototypes can reduce the errors caused by coding
program/subprocedure calls incorrectly.
One of the most common sources of difficult-to-debug errors
comes from having mismatched parameters between the
caller and the called routine.


Free-Form code

o Procedural language
o Easier to read (English-like)
o Blank lines allowed
o Longer comments permitted in-line with the RPG code
o Mixed case permitted
o Easier to maintain
o Easier to learn than fixed-format RPG
o More resembles modern programming languages
o Native ability to parse XML documents
* XML-INTO
* XML-SAX


File handling

o Unlimited number of files can be defined in a program

o RPGIV allows renaming all fields within a record format
at the file level with one line of code

Examples:

Prefix( AA : 2 ) changes the current field prefix to 'AA',
thus SDDOCO becomes AADOCO

Prefix(AA) prepends 'AA' to the existing field names,
thus SDDOCO becomes AASDDOCO

o User-opened files can be overridden to other files with
EXTFILE keyword, eliminating the need to use
OVRDBF before calling the program

Data Structures

o Unlimited number of data structures can be defined

o RPGIV allows renaming all fields within a externally-defined
data structure with one line of code

Example: Prefix( AA : 2 )

o By using Prefix('XX') to rename fields within a data structure,
ability to define an multiple external data structures over the
same file without errors caused by duplicate field names
in the data structures.

o Qualified data structures make code more readable.

o Key data structures
* LikeRec (see PDC4701A)

o Read a record from a file directly into a data structure
* LikeRec (see PDC4701A)

o Write a record to a file directly from a data structure
* LikeRec (see PDC4701A)

o Except for the DSTXT data structure, it is unnecessary
to specify From & To positions for subfields -
only subfield lengths need to be specified

o LikeDS allows defining new data structures
the same as existing data structures

o Overlay keyword simplifies overlaying fields within a data structure
* Overlay an array over data structure subfields
* Data structure arrays can be sorted
* Data structure arrays can be sorted by a sub-field


Variables

o Underscore character permitted in variable names

o Long variable names allowed (up to 4096 characters in length)
* Self-documenting

o Longer variables (up to 65535 characters)

o More data types allowed
* Pointer support

o INZ keyword allows work field initialization in D-specs

o On D-spec field definition, LIKE keyword allows defining
fields similar to existing fields
(similar to *LIKE DEFN in RPG/400)

o Indicators
* Named Indicators make code easier to read
* Less dependence on indicators - an RPGIV program
can usually be written without using /any/ indicators


Access to iSeries / System i / IBM i operating system resources

o Ability to use C run-time library functions

* Simplifies executing CL commands from within RPG programs

* Ability to directly manipulate (read, write, update) stream files
in the IFS (and QNTC or NFS) from RPG programs

o Access to System API's and MI built-in functions

o Access to Java Functions (See existing program Pxxxxxx)


RPGIV allows recursion


New Operation Codes

o EVAL
o EVALR
o CALLP
o CALLB
o XML-INTO (free-form only)
o XML-SAX (free-form only)


RPGIV Built-In Functions (BIF's)

(approximately 90 currently available)

o Date-and-time functions

o Data conversion and string-handling functions are
easier to read and understand, simplify coding

* %SUBST
* %REPLACE
* %TRIM
* %EDITC
* %CHAR
* %DEC
* %ADDR


Expressions

o Ability to specify complex mathematical expressions in a single line of
code

o Logical expressions easier to understand

Examples:
If %EOF ( FILE ); {used for READ operations}
If %EQUAL ( FILE ); {used for SETLL operations}
If %FOUND( FILE ); {used for CHAIN operations}

o Character expressions

Example:
Message = 'File ' + FileName + ' not found';


Arrays/Tables

o Unlimited number of Arrays and Tables
o Enhanced array and table handling
* More elements
* Longer elements
* Multidimensional arrays

Better exception and error handling capabilities

o MONITOR - ENDMON operation codes

o Operation extenders reduce (eliminate) dependence on
indicators for detecting errors, making code easier to
read and maintain

Example:

READ(E) FILE;
If %Error();
// do something
EndIf;










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