[This message was posted by Alessio Mazzanti of List <[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/eb69431a - PLEASE DO NOT REPLY BY MAIL.]
Sorry David, I would need another particular detail: As you replied to the question number 2, the mantissa and exponent parts have to be treated as two individual fields in the dictionary, and they will be somehow combined... My doubt is: how should I combine the status (assigned, undefined, empty) of the exponent and the mantissa when I combine them into a scaled number or similar? In particular do I have to expect the exponent is assigned and the mantissa is not and/or vice versa? Thanks in advance. Regards, -- Ale > 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. 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