Re: RPG Error or ?

Henrik,

In RPG there is no concept of "null", or "no value" (same thing).
So any debate on how to interprete "empty string" and "null" is moot, within
the context of RPG.

What you are describing are RPG semantics, which where in place since the
beginning of time, when there where only fixed length fields.
Now we also have varying, C-like strings, etc.


The RPG semantics for comparing two "strings", or two fixed character
fields, or varying length fields, etc, are always and consistently
"converted" to comparing two fixed length fields. And the RPG semantics are
that the shortest field is padded with blanks up to the length of the
longest field. This is not a bug, but a feature. So '' is not an empty
string, but a string with zero, one, two etc blanks, if it's compared to
another character value. This is the same answer given already multiple
times on this thread.


On Tue, Oct 11, 2011 at 4:52 PM, Henrik Rützou <hr@xxxxxxxxxxxx> wrote:

To me it isn't logical,

if you reset a variable field to "no value" you do it with

string = '';

%len(string) will display 0

so why is a compare with '' not equal to the setting of the field while
it (whatever there may be in memory) works if you do

string = 'abc';
if string = 'abc'; // will pass

string = 'abcd';
if string = 'abc'; // will fail

?

I have of course just changed my code to %len(string) > 0;





On Tue, Oct 11, 2011 at 4:40 PM, <rob@xxxxxxxxx> wrote:

If I change it to:
string = x'0515' + 'abc';
string='';
and debug it on an active line after the above I get
00000515 81828300 - ....abc

but if I change it to:
/free
*inlr=*on;
string='';
then none of the DSPLY's kick in, and

EVAL string :x

00000000 00000000 00000000 00000000 - ................
so, apparently
00050515 81828300 00000000 00000000 - ....abc........
is less than
00000000 00000000 00000000 00000000 - ................

Rob Berendt
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http://www.dekko.com





From: Henrik Rützou <hr@xxxxxxxxxxxx>
To: "RPG programming on the IBM i / System i" <rpg400-l@xxxxxxxxxxxx

Date: 10/11/2011 10:00 AM
Subject: RPG Error or ?
Sent by: rpg400-l-bounces@xxxxxxxxxxxx



Is it me that has misunderstood something or what would you expect
displayed from this code:

d string s 52a varying

string = x'0515' + 'abc';
or
string = x'4015' + 'abc';

// dosn't work (but works if x'4040' + 'abc')
if string > '';
dsply 'hello 1';
endif;

// works
if string <> '';
dsply 'hello 1';
endif;

// works
if %len(string) > 0;
dsply 'hello 2';
endif;


--
Regards,
Henrik Rützou

http://powerEXT.com <http://powerext.com/>
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Henrik Rützou

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