IBM AS/400 manual Using the Callp Operation, ¹ Subprocedures in the same module

Using

a

Prototyped

Call

Table

10.

Parameter Passing Options

Parameter

Option

Prototyped

Not

See

Page

Prototyped

Compile-time

parameter

Yes

135

checking

Pass

by

reference

Yes

Yes

135

Pass

by

value

Yes

(b)

136

Pass by read-only referenceYes

137

Pass

operational

descriptorsYes

(b)

Yes

(b)

138

Pass

*OMIT

Yes

(b)

Yes

(b)

139

Control

parameter

omission

Yes

Yes

140

Get number of passed parameY-s

Yes

141

ters

Disallow

incorrect

parameterYes

145

length

Note:

(b)

–

applies to

bound

procedures

only.

Using a Prototyped

Call

A

prototyped

call

is

one for which

there

is

a prototype that is a

eter checking. It has a much simpler call interface

and

offers

more

example,

using a

prototyped

call

you can

call

(with

the

same syntax)

¹

Programs

that

are

on

the

system

at

run

time

¹

Exported

procedures

in other modules or service programs that

are

the same

program

or

service

program

¹Subprocedures in the same module

In RPG,

prototyped calls

are also

known

as Freefree-form -callform

callsrefers.

to

the call syntax where the arguments for the

call

are specified

usi

syntax, much like the arguments

for

built-in

functions.

It

contrasts

wi

call,

where

the

arguments

are placed in separate specifications. The

ways

to

make a free-form

call,

depending on

whether

there is

a

ret

to be used. If there

is no return value, use the

CALLP

operation.

and you want to use the

value that is returned, then place the pr

within

an

expression,

for

example, with EVAL. If you

use

CALLP

to

a

that

returns

a

value,

the

return

value

is

ignored.

Note:

Only

prototyped

procedures

can

return

values;

prototyped

programs

For information on passing prototyped parameters, see “Passing Prototype Parameters” on page 135.

Using the CALLP Operation

You use the CALLP (Call a Prototyped procedure) operation to call a p program or procedure written in any language. The CALLP operation uses lowing free-form syntax:

C CALLP NAME{ (PARM1 {:PARM2 ... }) }

Chapter 10. Calling Programs and Procedures133