Hi, I'm working on a little library to trade bitcoins via the MtGox API. https://github.com/peterjoel/auto-trader I haven't got very far yet, but I feel like I'm already overcomplicating things, especially the module structure. The reason it has so many modules, even though there is hardly any code, is partly because I wanted to expose the properties of the MtGoxTicker record as lenses, without polluting the namespace with the underlying _accessors. Is this good or is there a more usual way of dealing with the problem? The other problem I'm facing is with name collisions for record accessors. There are two versions of MtGoxTicker from different services - one with a subset of the properties, which is supposed to be faster (it isn't, but that isn't the point). The data types are here https://github.com/peterjoel/auto-trader/blob/6974d66ae51459479c19be291d075b.... One is commented one out while I decide what to do. What is the best way to model those records to avoid collisions, while not being confusing to users of the library? I am very tempted to use type classes, but that feels naughty. Using unique prefixes seems bad too - it would be nice for some code to be able to use them interchangeably if they don't need all the fields. Is it possible to use unique names for the actual record accessors, but share the names of their lenses? Thanks, Peter
You can export specific pieces explicitely, ie: module AutoTrader.MtGox.Types (MtGoxTicker(MtGoxTicker), tkLast, tkLastAll, etc...) where and it will not export the _ field accessors. It is a hassle, but that's the price you pay for all that code generation. As for the two versions of MtGoxTicker, if they have a lot in common, you might think about using type classes for that. class BasicInfo a where tkHigh :: Lens a a MtGoxPrice MtGoxPrice tkLow :: Lens a a MtGoxPrice MtGoxPrice -- ... class ComplexInfo a where tkAvg :: Lens a a MtGoxPrice MtGoxPrice -- ... data MtGoxTickerBrief = MtGoxTickerBrief { _briefHigh :: MtGoxPrice, _briefLow :: MtGoxPrice } data MtGoxTickerFull = MtGoxTickerFull { _fullHigh :: MtGoxPrice, _fullLow :: MtGoxPrice, _fullAvg :: MtGoxPrice } makeLenses ''MtGoxTickerBrief makeLenses ''MtGoxTickerFull instance BasicInfo MtGoxTickerBrief where tkHigh = briefHigh tkLow = briefLow instance BasicInfo MtGoxTickerFull where tkHigh = fullHigh tkLow = fullLow instance ComplexInfo MtGoxTickerFull where tkAvg = fullAvg I'm sure there are other ways of dealing with it, but this works.
Hi Peter, Am 7/2/2013 12:52 AM, schrieb Peter Hall:
The other problem I'm facing is with name collisions for record accessors. There are two versions of MtGoxTicker from different services - one with a subset of the properties, which is supposed to be faster (it isn't, but that isn't the point). The data types are here https://github.com/peterjoel/auto-trader/blob/6974d66ae51459479c19be291d075b.... One is commented one out while I decide what to do. What is the best way to model those records to avoid collisions, while not being confusing to users of the library? I am very tempted to use type classes, but that feels naughty. Using unique prefixes seems bad too - it would be nice for some code to be able to use them interchangeably if they don't need all the fields.
This sounds like a good case for two separate modules: AutoTrader.MtGox.Ticker.Full would have a data Ticker = Ticker { .. } which is the commented-out MtGoxTickerFull, and AutoTrader.MtGox.Ticker.Fast would balso have a 'data Ticker = ...', which would be your MtGoxTicker. This would allow you to use the same field names without getting clashes, users of your library could choose hwo to import the types, i.e. what prefix to use - and people using no fields from the full ticker could switch their code by changing something like import qualified AutoTrader.MtGox.Ticker.Full to import qualified AutoTrader.MtGox.Ticker.Fast As a side note, I think that in the vast majority of cases where you think that a type class is be a good solution - it's not. :-} -- Frerich Raabe - raabe@froglogic.com www.froglogic.com - Multi-Platform GUI Testing
As a side note, I think that in the vast majority of cases where you think that a type class is be a good solution - it's not. :-}
This has been said a lot, which is why I was looking for suggestions. I
didn't think about separating them into different modules. It might work.
I think, for now, I'm going to keep it simple and just use the "fast" case
and worry about how to refactor to use both, when it comes to it.
Peter
On 2 July 2013 08:13, Frerich Raabe
Hi Peter,
Am 7/2/2013 12:52 AM, schrieb Peter Hall:
The other problem I'm facing is with name collisions for record
accessors. There are two versions of MtGoxTicker from different services - one with a subset of the properties, which is supposed to be faster (it isn't, but that isn't the point). The data types are here https://github.com/peterjoel/**auto-trader/blob/** 6974d66ae51459479c19be291d075b**bdeb718b53/AutoTrader/MtGox/**Types.hshttps://github.com/peterjoel/auto-trader/blob/6974d66ae51459479c19be291d075b... . One is commented one out while I decide what to do. What is the best way to model those records to avoid collisions, while not being confusing to users of the library? I am very tempted to use type classes, but that feels naughty. Using unique prefixes seems bad too - it would be nice for some code to be able to use them interchangeably if they don't need all the fields.
This sounds like a good case for two separate modules:
AutoTrader.MtGox.Ticker.Full would have a data Ticker = Ticker { .. } which is the commented-out MtGoxTickerFull, and AutoTrader.MtGox.Ticker.Fast would balso have a 'data Ticker = ...', which would be your MtGoxTicker.
This would allow you to use the same field names without getting clashes, users of your library could choose hwo to import the types, i.e. what prefix to use - and people using no fields from the full ticker could switch their code by changing something like
import qualified AutoTrader.MtGox.Ticker.Full
to
import qualified AutoTrader.MtGox.Ticker.Fast
As a side note, I think that in the vast majority of cases where you think that a type class is be a good solution - it's not. :-}
-- Frerich Raabe - raabe@froglogic.com www.froglogic.com - Multi-Platform GUI Testing
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Peter Hall
Hi, I'm working on a little library to trade bitcoins via the MtGox
API.https://github.com/peterjoel/auto-trader Are you aware of Adi Shamir's et.al. paper and its implications? Basically, they discovered it's a shell game fraud. (search terms: "bitcoin shamir").
How did you come to this conclusion?
You mean this paper, right?
http://eprint.iacr.org/2012/584.pdf
I read that paper, and I had some computer science classes in university, but I didn't see anything that hints at shell game fraud, nor did I find anything related to shell games, nor anything related to fraud. A search for "bitcoin shell game fraud" didn't provide any useful information...
-Michael
Am 06.07.2013 um 23:35 schrieb Will Ness
Peter Hall
writes: Hi, I'm working on a little library to trade bitcoins via the MtGox
API.https://github.com/peterjoel/auto-trader
Are you aware of Adi Shamir's et.al. paper and its implications? Basically, they discovered it's a shell game fraud. (search terms: "bitcoin shamir").
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participants (5)
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David McBride -
Frerich Raabe -
Michael Peternell -
Peter Hall -
Will Ness