Snippets tagged domain modelling
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Tesco in 70 lines of code
Domain model for the Tesco checkout implemented in F# using discriminated unions (in 20 lines of code) and console-based user interface for scanning products and calculating the total price.
5 people like this
Like the snippet!Posted: 12 years ago by Tomas Petricek
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Simple CQRS Inventory
a simple CQRS example, inspired by the blogpost http://tojans.me/blog/2014/02/26/cqrs-and-functional-programming/
6 people like this
Like the snippet!Posted: 7 years ago by Andreas Vilinski
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Finalizing Tesco purchase
The sample shows two different reprezentations of Tesco checkout. The first one stores scanned items - as a list of either purchase or cancel items - and the second stores final bill with product and total quantity. The snippet implements transformation that corresponds to finalizing the purchase.
3 people like this
Like the snippet!Posted: 12 years ago by Tomas Petricek
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C#-Friendly Single-Case Discriminated Unions
Single-case Discriminated Unions (https://fsharpforfunandprofit.com/posts/designing-with-types-single-case-dus/) are a lightweight way to create types for important concepts in your domain. Unfortunately, there's a few gotchas when consuming from C# to be aware of. For one, if you use the `==` or `!=` operators in C#, it will do a reference comparison, which is almost certainly not what you want for these wrapper types. By overriding `op_Equality` and `op_Inequality`, this will force it to use a structural comparison. Secondly, when using string concatenation via `+`, `String.Format`, or string interpolation, C# will implicitly convert non-string arguments to a string via `ToString`. This means if you forget to use `.Item` to unwrap your value, you will not get a compiler error, it will just implicitly call `ToString`, which by default will look like this: `Id "c148b684-2c40-4383-a1b9-0e8f37752fd0"`. By overriding `ToString`, we can make sure it will look like the raw underlying type when converted to a string: `c148b684-2c40-4383-a1b9-0e8f37752fd0`.
2 people like this
Like the snippet!Posted: 6 years ago by Justin Hewlett