Michael Diamant michaeldiamant
michaeldiamant
/ dependentTypeEvents.scala
Created
January 10, 2016 19:56
Use dependent types to represent a relationship between a command and its possible failures and successful outcomes (i.e. events). This representation encodes the relationship into the data types rather than a service-like interface.
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| object E1 { | |
| // Encoding a 1:1 command to event example | |
| sealed trait Event | |
| case class E1(i: Int) extends Event | |
| case class E2() extends Event | |
| sealed trait Intent[Z <: Event] { | |
| type Out = Z | |
| } | |
| case class C1(id: Int) extends Intent[E1] | |
| case class C2(id: Int) extends Intent[E1] |
michaeldiamant
/ gist:0cbab8984b6c84daa9c7
Created
December 10, 2015 15:09
Ansible unable to check for undefined vars using with_items
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| [michael@dca-infra01 ansible]$ cat /home/michael/ntoggle/ansible/roles/ntoggle.helix-service/tasks/required_vars.yml - name: check required variables are defined | |
| fail: msg="Variable '{{ item }}' is undefined" | |
| when: item is not defined | |
| with_items: | |
| - foo | |
| - bar | |
| - fail: msg="foo" | |
| when: foo is not defined | |
michaeldiamant
/ gist:3849746
Created
October 7, 2012 21:55
Tagged types representing units of price
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| trait Usd | |
| trait Eur | |
| trait ProfitCalculator[T] { | |
| def calculateProfit(executionPrice: BigDecimal @@ T, requestedPrice: BigDecimal @@ T): BigDecimal @@ T = | |
| tag(executionPrice - requestedPrice) | |
| } |
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| case class UsdPrice(value: BigDecimal) { | |
| def +(p: UsdPrice) = UsdPrice(value + p.value) | |
| def -(p: UsdPrice) = UsdPrice(value - p.value) | |
| } | |
| case class EurPrice(value: BigDecimal) { | |
| def +(p: EurPrice) = EurPrice(value + p.value) |
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| trait ExtensibleTradeExecutionProcessor extends TradeExecutionProcessor { | |
| val requestedTradeRepository: RequestedTradeRepository | |
| val priceMutators: Set[(RequestedTrade, BigDecimal) => BigDecimal] | |
| def process(requestId: String, executionPrice: BigDecimal): Option[ExecutedTrade] = | |
| for { | |
| requestedTrade <- requestedTradeRepository.findById(requestId) | |
| reportedPrice <- priceMutators.foldLeft(executionPrice)((price, mutator) => mutator(requestedTrade, price)).some | |
| } yield |
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| trait ComplectingTradeExecutionProcessor extends TradeExecutionProcessor with MarkupApplicator { | |
| val requestedTradeRepository: RequestedTradeRepository | |
| val markingUpSymbol: String | |
| val symbolMarkup: BigDecimal | |
| val markupVolumeThreshold: Long | |
| val volumeMarkup: BigDecimal | |
| def process(requestId: String, executionPrice: BigDecimal): Option[ExecutedTrade] = | |
| requestedTradeRepository.findById(requestId) |
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| trait MonadicStyleNewOrderResolver extends NewOrderResolutionErrors { | |
| val symbolDao: SymbolDao | |
| val marketTakerDao: MarketTakerDao | |
| val marketMakerDao: MarketMakerDao | |
| def resolve(order: NewOrder): Validation[String, ResolvedNewOrder] = | |
| for { | |
| symbol <- symbolDao.findByName(order.symbolName) | |
| .toSuccess(UnknownSymbol) |
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| trait JavaStyleNewOrderResolver extends NewOrderResolutionErrors { | |
| val symbolDao: SymbolDao | |
| val marketTakerDao: MarketTakerDao | |
| val marketMakerDao: MarketMakerDao | |
| def resolve(order: NewOrder): Either[String, ResolvedNewOrder] = { | |
| val symbol = symbolDao.findByName(order.symbolName) | |
| if (symbol.isEmpty) { | |
| return Left(UnknownSymbol) |