Presentation © Copyright 2002, Bryan Meyers Arithmetic and Assignment Operations Chapter 4.

Presentation © Copyright 2002, Bryan Meyers

Arithmetic and Assignment Operations

Chapter 4

Programming in RPG IVThird Edition

2

Objectives

• Perform arithmetic calculations in your programs

• Determine the appropriate size for numeric fields

• Determine how to round calculations to avoid truncation

• Convert data types• Use numeric and character literals; and

figurative constants


3

Simple Numeric Assignment

• Assigning a value to a field simple means giving a field a value

• EVAL is used to assign values to fields– Evaluates the expression to the right of the equal sign– Stores value in the field to the left of the equal sign

• Coding EVAL is optional with Version 5 free-format

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8CL0N01Factor1+++++++Opcode(E)+Extended-factor2+++++++++++++++++++++++++++++ // Free-format (Version 5 or later) /FREE EVAL Result_field = expression; /END-FREE

// Fixed-format (pre-Version 5) C EVAL Result_field = expression


4

Using EVAL for Arithmetic

• Single expression can contain as many arithmetic operators, numeric literals, and numeric fields to accomplish a desired calculation

• Left of ‘=‘ is a numeric field, to the right can be numeric fields or numeric literals

• Rules of precedence are used to determine order of math operations


5

Determining Field Sizes

Arithmetic Operation

Rule of Thumb Example

Addition Result should be one digit longer than longest factor

999

+999

1998

Subtraction Result should be as long as longest factor 999

-1

998

Multiplication Result field length should be the sum of the digit lengths of the factors

999

x999

998001

Division Result field should be the sum of the digit length of the factors

999 / .1 = 9990


6

Rounding (Half-Adjusting)

• To round, place an ‘H’ in the operation extender on the EVAL– Free-format specification requires explicit EVAL

when using an extender (Version 5)• Round only when necessary

– The RPG compiler will issue a warning message about unnecessary half-adjusting

– Unnecessary rounding reflects poorly on your programming skills and/or style

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8 /FREE EVAL(H) Interest = LoanAmt * StdRate; EVAL(H) Interest = AltAmt * PrimeRate; /END-FREE


7

Improving EVAL Precision

• To ensure that EVAL doesn’t truncate significant decimal places, use “Result Decimal Positions” option for expressions– Specify EXPROPT(*RESDECPOS) in H spec, to set

default option for program– Or, specify (R) extender for a single EVAL statement

• Otherwise system defaults to EXPROPT(*MAXDIGITS) option

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8H EXPROPT(*RESDECPOS)

/FREE EVAL(HR) Pay = HourlyRate * 40 + 1.5 * HourlyRate *(HoursWorked -40); /END-FREE


8

Sample Program - F Specs

*..1....+....2....+....3....+....4....+....5....+....6....+....7....+....8

// **********************************************************************

// This program calculates selling prices for received items based on a

// 60% markup over item cost. It also determines projected gross profit

// for each item in the shipment and total gross profit for all the items

// **********************************************************************

FNewItems IF F 40 DISK

FQPRINT O F 132 PRINTER


9

Sample Program - D & I

*..1....+....2....+....3....+....4....+....5....+....6....+....7....+....8

// Definition of all work fields used in program

D UnitProfit S 6 2

D SellPrice S 7 2

D GrssProfit S 10 2

D TotProfit S 14 2

// Input file of received items defined within the program

INewItems NS

I 1 30 Descript

I 31 36 2ItemCost

I 37 40 0QtyRcvd


10

Sample Program - C Specs

*..1....+....2....+....3....+....4....+....5....+....6....+....7....+....8

/FREE

EXCEPT Headings;

READ NewItems;

DOW NOT %EOF;

EVAL(H) UnitProfit = ItemCost * .6;

SellPrice = ItemCost + UnitProfit;

GrssProfit = UnitProfit * QtyRcvd;

TotProfit = GrssProfit + TotProfit;

EXCEPT Detail;

READ NewItems;

ENDDO;

EXCEPT TotalLine;

*INLR = *ON;

RETURN;

/END-FREE


11

Sample Program - O Specs

*..1....+....2....+....3....+....4....+....5....+....6....+....7....+....8

OQPRINT E Headings 1

O UDATE Y 11

O 55 'GROSS PROFIT PROJECTION'

O 82 'PAGE'

O PAGE 87

O E Headings 2 1

O 52 'SELLING'

O 74 'PER UNIT'

O 88 'TOTAL'

O E Headings 2

O 10 'ITEM'

O 39 'COST'

O 51 'PRICE'

O 61 'QTY'

O 73 'PROFIT'

O 92 'GROSS PROFIT’


12

Sample Program - O Specs

*..1....+....2....+....3....+....4....+....5....+....6....+....7....+....8

O E Detail 1

O Descript 30

O ItemCost 1 41

O SellPrice 1 53

O QtyPcvd 1 62

O UnitProfit 1 74

O GrssProfit 1 92

O E TotalLine 1

O 70 'GRAND TOTAL GROSS PROFIT -

O PROJECTED:'

O TotProfit 1 92 '$'


13

Character Assignment

• EVAL is used in character assignment– Both sides of assignment expression must be character fields

or expressions

• Use a continuation character (+ or -) to continue a literal on the next line

• EVAL operation performs the assignment by transferring character by character, starting with the left-most character of the literal

• The result field is either padded with blanks or truncated

• May also use figurative constants– *BLANKS, *HIVAL, *LOVAL, etc.


14

Data Type Conversion: MOVE• MOVE operation transfers characters from Factor 2 field to the

Result, character by character, moving through the fields from right to left– MOVEL moves from left to right

• Disregards decimal position in numeric fields• To pad extra result positions with blanks, use (P) extender

– Good practice: match the size of the Result and Factor 2 fields• MOVE not supported by free-format

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8CL0N01Factor1+++++++Opcode(E)+Factor2+++++++Result++++++++Len++D+HiLoEq.... * Store a numeric value in character field Alpha (length 4)C MOVE 1234 Alpha

* Store character field Alpha in a numeric field (length 4, 0 decimals)C MOVE Alpha Numeric


15

Built in Functions (BIF)

• %ABS (Absolute Value)– Returns absolute value of expression, discarding

sign• %DIV (Divide)

– Integer division• %REM (Remainder)

– Determines remainder from integer division (modulus)

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8 /FREE TransTotal = %ABS(Debits - Credits); Hours = %DIV(Minutes:60); Minutes =%REM(Minutes:60); /END-FREE


16

Points to Remember

• EVAL operation can express complex arithmetic calculations in a single free-form expression

• Truncation is based on the location of the decimal positions

• EVAL is used to assign values to character fields• Operations MOVE and MOVEL are used to change

data type– Not support by free-format

• Built-in functions perform complex calculations, string operations, and data-type conversion in free-format expressions

Presentation © Copyright 2002, Bryan Meyers Arithmetic and Assignment Operations Chapter 4.

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