f# - Map and pattern matching -

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i have assignment here i'm struggling with:

type multimap<'a,'b when 'a:comparison , 'b:comparison> = mmap of map<'a, list<'b>>

the assignment states

we define canonical representation of multimap representation elements in value-lists ordered. declare function canonical: multimap<'a,'b> -> multimap<'a,'b> when 'a : comparison , 'b : comparison canonical m returns canonical representation of m.

right have:

let toorderedlist (mm:multimap<'a,'b>)  =      match mm     | mmap m ->

i don't know how pattern match on this. help? :3

ok, give answer function looking can written this:

let cannonical (mmap m) =      m      |> map.map (fun _ vs -> list.sort vs)      |> mmap

this deconstructs multimap right in argument definition (pattern-matching) , pipes map<> m through - sorting lists map.map , wrapping mulitmap using constructor mmap


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