Re: Moving Null to a Character variable

[Scott Klement <klemscot@xxxxxxxxxxxx>]

Hi Lakshmi,

> DbTLogonMsg       DS
> D bMsgCode                    5A
> D bMsgLen                        5A  INZ(' ')
>
> C MOVE     *BLANKS     bMsgCode
>
> I initialized one subfield with Blanks and Moved Blanks to another
> subfield.

After this code runs, both bMsgCode and bMsgLen are filled with spaces.
Is that what you're asking?  Or, what are you asking?


> In RPG, Moving Blanks and Moving NULL to a Character variable are same or
> different?
> If it is different, how to move NULL to a Character Variable?

When you say "NULL" what are you refering to?

Are you talking about database NULL value support?  (This is controlled in
RPG using the ALWNULL keyword on the H-spec and %nullind() BIF in the
calcs)

Is that what you mean?  If so, it's different from moving blanks to a
character field.  Blanks are still a value.  %nullind() is a separate
indicator that you can check that means "no value."

Are you talking about NULL pointers?  These are set and checked for by
comparing a pointer to the special value *NULL.

Is that what you mean?  If so, it's VERY different from setting the string
to blanks -- since whatever is based on this pointer has no memory, it
cannot be filled with spaces without the program crashing.

Are you talking about an empty varying string?  For example:

     D myString        s             10A   varying
     c                   eval      myString = ''

or, another way of doing the same thing:

     D myString        s             10A   varying
     c                   eval      %len(myString) = 0

Is that what you mean?  If so, it's different from moving blanks to a
string.  Moving blanks means that the string is 5 bytes long, each byte
contains a space character.  Space is unprintable, but it's still a
character x'40'.  For example:

     D bigString       s             20A
     D myString        s             10A   varying
     c                   eval      %len(myString) = 0
     c                   eval      myString = '
     c                   eval      bigString = 'Word1'+mystring+'Word2'

After that code runs, bigString will contain "Word1Word2"

However, if I move blanks to a fixed-length string:

     D bigString       s             20A
     D myString        s             10A
     c                   eval      myString = *blanks
     c                   eval      bigString = 'Word1'+mystring+'Word2'

After that code runs, bigString will contain 'Word1          Word2'

See the difference?  in the first case, there's no data in myString, so
when I concatenate it, it does not add anything to the string.  in the
second case, myString is full of spaces.  When I concatenate it, I add 10
spaces to the string.

I hope I answered your question.  Since I'm not clear on what you're
really asking, I actually answered 3 different questions.

Please clarify what you meant.