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| DFDL infix, prefix and postfix separators |
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| gfrench |
 Posted: Tue Nov 03, 2015 2:05 pm Post subject: DFDL infix, prefix and postfix separators |
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Acolyte
Joined: 10 Feb 2002
Posts: 71
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Can anyone give me examples of the last two? I got a great examples from maths
| Quote: |
infix (A * B)+(C/D)
prefix +(*AB)(/CD)
postfix (AB*)(CD/)+
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But how does that apply to message structure?
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| mqjeff |
| Posted: Tue Nov 03, 2015 2:40 pm Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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prefix is an indicator (a tag in MRM terminology).
postfix is also an indicator, possibly a terminator rather than an indicator.
it's really not a significant structural difference - unlike infix. It's really a matter of attributes on the structure holding the items.
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| timber |
| Posted: Wed Nov 04, 2015 12:54 am Post subject: |
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Grand Master
Joined: 25 Aug 2015
Posts: 1292
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'prefix' means 'occurring before'.
'postfix' means 'occurring after'.
'infix' means 'occurring between'.
In mathematics, these terms can be applied to operators like +, -, / and *.
In computer science, they can be applied to delimiters in a data format.
So a prefix delimiter looks like this:
an infix delimiter like this:
and a postfix delimiter like this:
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| mqjeff |
| Posted: Wed Nov 04, 2015 7:43 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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Dear sir Kimber...
The question was about how to model those in DFDL... I realize that's a complicated subject, and you might struggle with it...  
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| timber |
| Posted: Wed Nov 04, 2015 8:41 am Post subject: |
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Grand Master
Joined: 25 Aug 2015
Posts: 1292
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Mustering what little dignity remains...
I thought the OP was trying to understand what the terms prefix/postfix/infix mean. They tried Googling/Binging/Yahooing and found a reference to mathematical operators, which probably didn't help much. So I tried to explain how DFDL uses those words.
Your hit. Sir. |
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| mqjeff |
| Posted: Wed Nov 04, 2015 8:49 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| timber wrote: |
| Your hit. Sir. |
 
So, these are modelled in DFDL as initiators... ? terminators for infix/postfix?
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| gfrench |
| Posted: Wed Nov 04, 2015 9:27 am Post subject: |
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Acolyte
Joined: 10 Feb 2002
Posts: 71
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Thanks.. I think someone had over complicated it. After testing
a,b,c - infix
a,b,c - postfix with trailing suppression
a,b,c,d, - postfix no trailing suppression
,a,b,c - prefix
I wonder if you can have prefix, with first prefix suppression. (No I don't need an answer!) |
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| timber |
| Posted: Wed Nov 04, 2015 2:13 pm Post subject: |
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Grand Master
Joined: 25 Aug 2015
Posts: 1292
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| Quote: |
| I wonder if you can have prefix, with first prefix suppression. (No I don't need an answer!) |
But you're getting one anyway...
No, you cannot. That would be exactly the same as infix.
Delimiter suppression happens in one of two ways:
- the delimiters for all trailing empty elements are suppressed ( trailing means 'after the last mandatory element')
- the delimiters for all empty elements are suppressed
So you can't suppress a particular delimiter. It will be suppressed or not based on whether the corresponding element is empty ( and the delimiter suppression setting ).
btw, this looks wrong:
| Quote: |
| a,b,c - postfix with trailing suppression |
if the delimiter for the missing element d was *not* suppressed then it would be
a,b,c,,
So I think it should be
a,b,c,
Pedantic? Probably, but there's enough confusion in this area already, and I don't want to leave inaccurate posts on this forum to muddy the waters. |
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