Post navigation ← Unit testing Haskel code with HUnit Windows environment variables and folder locations → This entry was posted in Haskell on Jby purpleblob. In this case newTriangle is a copy of the triangle data, with the hypotenuse changed. We can declare instances of this type using names or without names, for example fixes the issue with using pattern matching – which ofcourse is still a valid way of doing things). It’s not clear what these fields of the constructors mean, so let’s add some names which also allows us to more easily access specific values from the data (i.e. So for example here we have a data type Shape with constructors for Circle and Triangle.ĭata Shape = Triangle Int Int Int | Circle Int We can combine types just as we combined False and True into essentially a union. Note: The type annotation is not required and the underscore is a discard, hence is ignored. example of printing the x value of value pt of type Point
In this example we could create a point as followsĪccessing these values can be a little verbose (especially when we might have lots of fields) because of the lack of any names, hence we’d use pattern matching, i.e. We can also declare types more like structs/classes in that we can define the field types that make up the type. Note: The type name and the value constructor must be capital cased. The values after the = are the value constructors with the | being like an or, hence this Bool have either False or True value. So here’s the definition of a Boolean type We can create a simple data type using the data keyword, followed by either of available values (in C# this would be similar to an enum). Haskell is no different in offering these capabilities. These help with readability, modularity etc. In most programming language we need ways to declare our own types.
0 kommentar(er)
