Namespace

Syntax

namespace [rec] [parent.]identifier

• rec for recursive → see slide next

• parent for grouping namespaces

Content

An F♯ namespace can only contain local types and modules

• Cannot contain values or functions ❗

• By comparison, it's the same in C♯ with namespace that contains classes / enums only

What about nested namespaces?

• Only happens declaratively namespace [parent.]identifier

• 2 namespaces declared in the same file = not nested but independent

Scope

• Several files can share the same namespace

• Several namespaces can be declared in a single file

  • They will not be nested

  • May cause confusion ❗

☝ Recommendations \

• Only one namespace per file, declared at the top

• Organize files by grouping them in directories with the same name as the namespace

Level	Folder	Namespace
0 (root)	/	Root
1	/Lev1	Root.Lev1
2	/Lev1/Lev2	Root.Lev1.Lev2

🚀 Recursive namespace

Extends the default unidirectional visibility: from bottom to top → Each element can see all the elements in a recursive namespace.

namespace rec Fruit

type Banana = { Peeled: bool }
    member this.Peel() =
        BananaHelper.peel  // `peel` not visible here without `rec`

module BananaHelper =
    let peel banana = { banana with Peeled = true }

⚠️ Drawbacks: slow compilation, risk of circular references

☝ Recommendation: handy but only for very few use cases