RPGIVbestprac

8/7/2019 RPGIVbestprac

1/11

RPG IV Best Pract ices

Presented by Bryan Meyers

Copyright 2004, Bryan Meyerswww.bmeyers.net

Wors t Prac t ices

I want to use RPG IV, but I dont need ILE

Ill use RPG IV, but not free format

I dont have the time

If it aint broke

Best Prac t ices

Enforce RPG IV style standards

Use free-format RPG IV

Embrace ILE

Encourage modular design

Style Goals

Accelerate development process

Write with reuse in mind

Facilitate program maintenance

Write with standards in mind

Reduce errors

Write smaller, single-function compile units

Test smaller compile units

Style Goals

Eliminate duplicate code

Even little bits of it

Use procedures instead

Eliminate conditional logic

Hide it in procedures

Eliminate complex routines

Hide them in procedures

Eliminate old code

Free-Format Speci f ic a t ion

V5R1 alternative to C-specs

May be interspersed with C-specs

....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8/FREEChain(ne) EmployeeID Employees;Select;When %Error;Return;

When %Found;Eval(h) TotalPay = (RegHours * Rate) + (OvtHours * Rate * 1.5);

Endsl;/END-FREE


2/11


Code free-format statements between/FREE and /END-FREE directives

....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8/FREEChain(ne) EmployeeID Employees;Select;When %Error;Return;


Endsl;/END-FREE

Column 7....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8/FREEChain(ne) EmployeeID Employees;Select;When %Error;Return;


Endsl;/END-FREE


Code goes in columns 8-80

Columns 6-7 must be blank

Indenting is allowed

/FREEChain(ne) EmployeeID Employees;Select;When %Error;Return;


Endsl;/END-FREE


Statement can span several lines

Semicolon ends each logical line

Multiple statements per line not allowed


Statement begins with opcode

Opcode Factor1 Factor2 Result;

/FREEChain(ne) EmployeeID Employees;Select;When %Error;Return;


Endsl;/END-FREE


If statement doesnt begin with opcode

EVAL is assumed for assignment expressions

CALLP is assumed otherwise

/FREEEmpNbrErr = *OFF;CalcTaxes(EmployeeID:TotalPay);Eval(h) TotalPay = (RegHours * Rate) + (OvtHours * Rate * 1.5);/END-FREE

EVAL assumed

CALLP assumed /FREEEmpNbrErr = *OFF;CalcTaxes(EmployeeID:TotalPay);Eval(h) TotalPay = (RegHours * Rate) + (OvtHours * Rate * 1.5);/END-FREE


Opcode required when extender isnecessary

E.g., EVAL(H) or CALLP(E)

EVAL required


3/11


Indicator columns not supported

No conditioning indicators

Use structured opcodes instead

No resulting indicators

Use BIFs instead

No level indicators

Revert to fixed format to specify indicator


Free-format comments begin with //

May start anywhere from columns 8-80

Inline comments allowed

....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8/FREE// Calculate total pay for employeeChain(ne) EmployeeID Employees;If %Found; // If employee active, calculate total pay

Eval(h) TotalPay = (RegHours * Rate) + (OvtHours * Rate * 1.5);Endsl;/END-FREE

Comments


Fixed-format comments may also begin with//

Anywhere from columns 6-80

Inline comments not allowed

CL0N01Factor1+++++++Opcode(E)+Factor2+++++++Result++++++++Len++D+HiLoEq// Calculate tax for total transactionC TotTaxable MULT T axRate TaxAmount

Comment

Comments

Convert to // comments

Eliminate all * comments

Avoid right-hand "end-line" comments incolumns 81-100

But use inline // comments where appropriate

Comments

Use comments to clarify not echo yourcode

Brief program or procedure summary

Title for subroutine, procedure, or other sectionof code

Explain an obscure technique

Comments

Always include a brief summary at thebeginning of a program or procedure

Program or procedure title

Brief description of purpose

Chronology of changes

Summary of indicator usage (if any)

Description of the procedure interface

Example of how to call the procedure


4/11

Comments

Use consistent "marker line" comments todivide major sections of code

Use blank lines to group related source linesand make them stand out

// ---------------------------- Prototypes

Declarat ions

Declare all variables within D-specs

Organize D-specs consistently

Main prototype (PR)

Other prototypes (PR)

Procedure interface (PI)

Named constants (C)

Data structures (DS)

Standalone variables (S)

Data St ruct ures

Indent data item names to improvereadability and document data structures

Use length notation instead of positionalnotation in data structure declarations

Use positional notation only when the actualposition in a data structure is important

When defining overlapping fields, use theOVERLAY keyword instead of positional notation

Data St ruct ures

Use qualified data structuresD Customer DS QualifiedD Name 20D YTDSls 11 2D Vendor DS QualifiedD Name 20D YTDPurch 11 2 Dim(12)/FreeCustomer.YTDSls = 0;

/End-free

Data St ruct ures

Avoid multiple occurrence data structures

Use array data structures instead

D RegionSls DS Dim(50)D QualifiedD Name 20D MonthlySls 11 2 Dim(12)/FreeRegionSls(Region).MonthlySls(Month) = Totsls;

/End-free

Data St ruct ures

Use LIKEDS, LIKEREC, and externallydescribed data structures

FCustfile UF E K DiskD CustData DS Likerec(Custrec)


5/11

Data St ruct ures

Use data structures instead of key lists

FCustfile UF E K DiskD CustKey DS Likerec(Custrec:*Key)/FreeChain %KDS(CustKey) Custrec;

/End-free

Data St ruct ures

Avoid compile time arrays

Provide initial values in a data structure instead

D DaysData DSD 9 Inz(Sunday)D 9 Inz(Monday)D 9 Inz(Tuesday)D 9 Inz(Wednesday)D 9 Inz(Thursday)D 9 Inz(Friday)D 9 Inz(Saturday)D Days 9 Dim(7)D Overlay(DaysData)

Naming Convent ions

Be sure an items name fully and accuratelydescribes the item

Name lengths of 10 to 14 characters

User longer names (with ) only whennecessary

Naming Convent ions

Name a procedure after its return value

For subroutines, use a verb/object syntax

Or for procedures without a return value

Maintain a dictionary of names, verbs, andobjects

Naming Convent ions

Use mixed case to clarify the named itemsmeaning and use

Avoid using special characters (@, #, $)

Li tera ls and Constant s

Use named constants instead of literals

Except 0 and 1

D RecordLocked C 01211D FileClosed C 01218/FreeChain(e) %KDS(CustKey) Custrec;Select;When %Status = RecordLocked;

When %Status = FileClosed;

Endsl;/End-free


6/11

Li tera ls and Constant s

Use named constants instead of literals

Except 0 and 1

D RecordLocked C 01211D FileClosed C 01218/FreeMonitor;Chain %KDS(CustKey) Custrec;

On-error RecordLocked;

On-error FileClosed;

Endmon;/End-free

Ind ica to rs

Eliminate numbered indicators

Use named indicators instead

Use EVAL with *Inxx and *On or *Off insteadof SETON or SETOFF

Never use MOVEA to set multiple indicators

Dont use conditioning indicators ever

Ind ica to rs

Use functions to replace resulting indicators

Qualify functions where possible

Unless used in close proximity to where they areset

/FreeRead Custfile;If %Eof(Custfile);

Endif;/End-free

Ind ica to rs

Use an indicator data structure with DDSfiles

FWrkCustD CF E Workstn INDDS(Indicators)D Indicators DSD Exit 3 3ND Cancel 12 12N/FreeIf Exit Or Cancel;

*Inlr = *Off;Endif;/End-free

Structured Programming

Dont use GOTO, CABxx, or COMP

Dont use obsolete IFxx, DOUxx, DOWxx, orWHxx opcodes

Perform multipath comparisons withSELECT/WHEN/OTHER/ENDSL

Dont use CASxx opcode (obsolete)

Always qualify END opcodes

Use ENDIF, ENDDO, ENDSL

Str ing Manipu la t ion

Use a named constant to declare a stringconstant instead of storing it in an array or

table

Avoid using arrays and data structures tomanipulate character strings and text

Use EVAL whenever possible for stringmanipulation


7/11

Avoid Obsolescenc e

Dont sequence program line numbers incolumns 1-5

Avoid program-described files

Use free-format syntax for opcodes

If a function and an operation code do thesame thing, use the function

Avoid Obsolescenc e

Shun obsolete operation codes

ADD Use + operatorDIV Use / operator or %DIVMULT Use * operatorMVR Use %REMSQRT Use %SQRTSUB Use operatorXFOOT Use %XFOOTZ-ADD Use EVALZ-SUB Use EVAL

Avoid Obsolescenc e


CAT Use + operatorCHECK Use %CHECKCHECKR Use %CHECKRSCAN Use %SCANSUBST Use %SUBSTXLATE Use %XLATE

Avoid Obsolescenc e


MOVE Use %SUBST, expressions, BIFsMOVEA Use %SUBST, expressions, BIFsMOVEL Use %SUBST, expressions, BIFs

Avoid Obsolescenc e


ANDxx Use ANDCABxx Use expressionsCASxx Use SELECT/WHEN/OTHERCOMP Use expressionsDO Use FORDOUxx Use DOUDOWxx Use DOWIFxx Use IFORxx Use ORWHENxx Use WHEN

Avoid Obsolescenc e


CALL Use CALLPCALLB Use CALLPPARM Use PR/PI definitionsPLIST Use PR/PI definitions


8/11

Avoid Obsolescenc e


ADDDUR Use + operator, date BIFsEXTRCT Use %SUBDTSUBDUR Use operator, date BIFs

or use %DIFFTIME Use date BIFs

Avoid Obsolescenc e


ALLOC Use %ALLOCDEFINE Use D-specs with LIKEKFLD Use %KDS data structure (V5R2)KLIST Use %KDS data structure (V5R2)LOOKUP Use %LOOKUP or %TLOOKUPOCCUR Use array data structure (V5R2)REALLOC Use %REALLOCSETOFF Use expressionsSETON Use expressionsSHTDN Use %SHTDN

Avoid Obsolescenc e


BITOFF Use %BITAND, %BITNOT (V5R2)BITON Use %BITOR (V5R2)MHHZO Use %BITAND, %BITOR (V5R2)MHLZO Use %BITAND, %BITOR (V5R2)MLHZO Use %BITAND, %BITOR (V5R2)MLLZO Use %BITAND, %BITOR (V5R2)TESTB Use %BITAND (V5R2)TESTN Use MONITOR, ON-ERRORTESTZ Use %BITAND (V5R2)

Avoid Obsolescenc e


GOTO No alternativeTAG No alternative

Avoid Obsolescenc e

Dont mix free format with fixed format C-specs

CL0N01Factor1+++++++Opcode(E)+Factor2+++++++Result++++/FREE// Calculate total pay for employeeEmpNbrErr = *OFF;

/END-FREEC MOVEL(P) CpyNbr EmployeeIDC MOVE EmpNbr EmployeeID/FREEChain(ne) EmployeeID Employees;

/END-FREE

Misce l laneous Guide l ines

In all specifications that support keywords,observe a one-keyword-per-line limit

Leave column 7 blank in H- and D-specs


9/11

Modular Programm ing

Use prototypes to define parameters andprocedure interfaces

Even *ENTRY parameter lists

// --------------------------- Main procedure interfaceD Main PR EXTPGM('MYTRGPGM')D TrgBuffer 256D TrgBufferLen 10I 0D Main PID TrgBuffer 256D TrgBufferLen 10I 0


Store procedure prototypes in /COPYmembers

Or use conditional compilation

Include constant declarations in the same/COPY member as a modules prototypes

Use IMPORT and EXPORT only for globaldata items


Use binding directories consistently

*Combination of application-specific bindingdirectory and cross-application binding directory

Stick to a minimum number of bindingdirectories

CRTPGM PGM(MYPGM) BNDDIR(APPBNDDIR GENBNDDIR)


Control service program signatures withbinder language

STRPGMEXP PGMLVL(*CURRENT)EXPORT SYMBOL(DAYNBR)EXPORT SYMBOL(DAYNAME)

ENDPGMEXPSTRPGMEXP PGMLVL(*PRV)

EXPORT SYMBOL(DAYNBR)ENDPGMEXP CRTSRVPGM SRVPGM(DATSRVPGM)MODULE(*SRVPGM)

EXPORT(*SRCFILE)SRCFILE(QSRVSRC)SRCMBR(*SRVPGM)


Avoid running ILE programs in the defaultactivation group

DFTACTGRP(*NO)

ACTGRP(name)

ACTGRP(*CALLER) during OPM-ILE transition


Beware AG-related problems

Invalid override scope

Invalid shared ODP scope

RCLRSC errors


10/11


Convert reusable code to procedures Redundant routines, subroutines

Business-specific processing

/COPY members

Called programs


Store reusable *MODULE objects in acommon library Use consistent naming conventions

Use public documentation

The Last Word on Sty le

Once and only once

Lots of little pieces

Make it right before you make it faster Keep it right when you make it faster

Make it clear before you make it faster

Dont sacrifice clarity for small gains inefficiency

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