[This message was posted by David Rosenborg of Pantor Engineering AB <[EMAIL PROTECTED]> to the "FAST Protocol" discussion forum at http://fixprotocol.org/discuss/46. You can reply to it on-line at http://fixprotocol.org/discuss/read/c167bc59 - PLEASE DO NOT REPLY BY MAIL.]
Yes, if the previous value has the state empty and the bit is not set, then the exponent is NULL. /David > Thank you very much for your prompt and clear reply. > > Just a little question: what if the exponent bit isn't set and the > previous value is empty? Is this a particular case of NULL exponent? > > Regards, -- Ale > > > > > Ale - > > > > 1. No. Whether you should process the mantissa or not is only > > dependent on a single thing: if the exponent is NULL or not. > > Whether you use a operator on the exponent doesn't change this > > property. > > > > In your example you use the copy operator. If the bit is not set this > > means "copy the previous value". If the previous value is not NULL, > > then the value of the exponent is not NULL and the mantissa is > > present. > > > > 2. The mantissa and exponent parts are treated as two individual > > fields in the dictionary so there are one or two separate signed > > integer fields in the dictionary to manage. There is no > > corresponding scaled number field in the dictionary in this case. > > However, when you communicate the value of the field from the > > decoder to the application you would typically combine them into a > > scaled number or similar. > > > > /David > > > > > Actually may be I was not so clear. > > > > > > In the specific case: > > > > > > < decimal name="MDEntryPx" id="270" presence="optional" > < > > > exponent > > > > < copy value="-2" / > < / exponent > < mantissa > < delta / > < / > > > mantissa > < /decimal > > > > > > > since the decimal is optional, then the exponent is optional. > > > Moreover, since the exponent has the individual copy operator, > > > then the exponent will have a bit in the pmap (no matter if it is > > > set or not). > > > > > > The exponent will be considered absent in two distinct cases: > > > > > > a) The bit is not set. > > > b) The bit is set but, since the exponent is optional, it is present > > > in the stream in its NULL representation. > > > > > > In both these cases the mantissa will be not present in the stream > > > as well and has to be considered absent. > > > > > > The only case in which the mantissa is present in the stream is when > > > the exponent bit in pmap is set and the exponent value is not NULL. > > > > > > 1. Is all that right? > > > > > > 2. How should we set the new previous value of the decimal (the > > > corresponding Scaled Number) if the exponent has to be considered > > > absent? > > > > > > > > > > > > Note that even if the exponent bit in pmap was not set, the value of > > > the exponent field could result assigned (for example it should be > > > assigned to the copy initial value, or to the previous value stored > > > in the dictionary). > > > > > > 3. Let suppose the mantissa is not in the stream (because of the > > > exponent absence), what does it imply in term of the mantissa field > > > value, and what in term of the mantissa new previous value? > > > > > > > > > Many thanks in advance. > > > > > > Regards, -- Ale > > > > > > > > > > > > > Ale - > > > > > > > > A bit in the pmap indicates how a field operator should be > > > > executed. The exact meaning of the bit is dependent on the > > > > operator type and its attributes. > > > > > > > > The bit doesn't automatically indicate whether an optional field > > > > is NULL or not. Only after exercising the operator according to > > > > the bit you'll know if the value is NULL or not. > > > > > > > > When using a decimal field with individual operators, and the > > > > value of an exponent field is NULL, the instruction for the > > > > mantissa should be skipped. > > > > > > > > You may want to have a look a this post (and other posts in the > > > > same thread): > > > > > > > > http://www.fixprotocol.org/discuss/read/24ed599c > > > > > > > > /David > > > > > > > > > > > > > Hello, I would need a clarification. > > > > > > > > > > The handbook [section 10.5.1 -- Presence Map and NULL > > > > > Utilization] says: > > > > > > > > > > [...]If the decimal has optional presence, the exponent field is > > > > > treated as an optional integer field and the mantissa field is > > > > > treated as a mandatory integer field. The presence of the > > > > > mantissa field and any related bits in the presence map are > > > > > dependent on the presence of the exponent. The mantissa field > > > > > appears in the stream iff the exponent value is considered > > > > > present. If the mantissa has an operator that requires a bit in > > > > > the presence map, this bit is present iff the exponent value is > > > > > considered present.[...] > > > > > > > > > > Let suppose I have the following decimal field in my template > > > > > definition: > > > > > > > > > > < decimal name="MDEntryPx" id="270" presence="optional" > < > > > > > exponent > > > > > > < copy value="-2" / > < / exponent > < mantissa > < delta / > > > > > > > < / > > > > > mantissa > > > > > > < /decimal > > > > > > > > > > > For the best of my comprehension in this case the exponent is > > > > > optional, and has its own bit in pmap (due to the copy > > > > > operator). If that bit is not set (the exponent is not present > > > > > in the stream for sure) then the mantissa will be not present in > > > > > the stream as well. > > > > > > > > > > 1. Does the same worth if the bit in pmap is set but the > > > > > exponent value is NULL? > > > > > 2. What about the new previous value of the Scaled Number if the > > > > > exponent has to be considered absent? > > > > > > > > > > Moreover, the fact that the exponent bit in pmap is not set > > > > > should not imply that the value of the exponent field will be > > > > > not assigned (e.g. it should be assigned to the copy initial > > > > > value, or to the previous value stored in the dictionary). > > > > > > > > > > 3.Let suppose the mantissa is not in the stream (because of the > > > > > exponent absence), what does it imply in term of the mantissa > > > > > field value, and in term of the mantissa new previous value? > > > > > > > > > > Many thanks in advance. Kind regards, -- Ale [You can unsubscribe from this discussion group by sending a message to mailto:[EMAIL PROTECTED] --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Financial Information eXchange" group. To post to this group, send email to FIX-Protocol@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/FIX-Protocol?hl=en -~----------~----~----~----~------~----~------~--~---
