Re: Procedure Examples VR7.1

On 2/1/2017 2:47 PM, Scott Williams wrote:

I'm attempting to create a very simple procedure that converts a given
numeric value into another. In this case, a value in Celsius to be
converted to Fahrenheit.

The RPG manual is your 'go-to' reference, but you can also check out the
old but still very useful ILE 'Sorcerer's' Redbook.

I can't seem to get my PR and PI sorted out, and/or the positioning of

the

P spec decs.

You have it right.

The 'PR' indicates a prototype. The prototype is a way to tell the
compiler about a procedure; what its name is, what sort of variable (if
any) it returns, what parameters (if any) it takes as input.

The P-specs enclose the actual procedure.

HDFTACTGRP(*NO)
HMAIN(C2F)
D CVT2F PR 5S 2 EXTPROC('C2F')
D
D $C 5S 2 VALUE

D$F S 5S 2

/FREE
$F = C2F($C);

Guessing you have a '$C undefined' error here. That's because the
parameter names on the PR specs aren't actually defining variables -
they are... documentation. So there is no $C defined in the mainline of
this program. Just like the code defines $F, it needs to define $C.
More interestingly, the names in the mainline don't need to be the same
as those in the sub-procedure.

Once you define $C (try something like input_c) you'll need to assign a
value to it. You can do that in the D specs or in the calcs, but either
way, in order to get Fahrenheit out, you'll need to send Celsius in.

Because the code specifies 'VALUE' on the parameter, you can pass in a
literal; the compiler will handle the conversion from literal to 5s 2
for you. So you could skip defining $C altogether and do this:

$f = c2f(25);

DSPLY $F;
*INLR = *ON;
/END-FREE

PC2F B EXPORT
DC2F PI 5S 2
D $C 5S 2 VALUE
D$F S 5S 2
/FREE
$F = (($C * 1.8) + 32);
RETURN $F;
/END-FREE
P E

Do I create this as a module, or a bound program?

I'd create it with CRTBNDRPG. As-written, the EXPORT is extraneous.
EXPORT means that you want other programs to be able to execute this
sub-procedure. Generally speaking, I'd advise that if you want to do
that, you put it into a service program rather than a program.

But for starting out, what you have is the perfect vehicle for
experimentation. Once you become comfortable with the infrastructure of
PI/PR, etc it's another very useful exercise to move those
sub-procedures into a service program. But for now, one step at a time :-)

--
--buck

Try wiki.midrange.com!

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