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How to translate this to F#?
f#

Hello,

I can't translate this C# function to F#:

public static Dictionary<A,B> Clone (Dictionary<A, B> dic) { var ret = new Dictionary<A, B>(); foreach(var x in dic) { ret[x.Key] = x.Value; } return ret; } The problem is I can't replicate in F# the work done by foreach. In C#, the type of x is System.Collections.Generic.KeyValuePair<A, B>. If F# I can only call methods in the Dictionary class; and among these methods I can't find one which iterates the dictionary passing a KeyValuePair. Thanks for any help

.

Here are a couple ways:

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open System.Collections.Generic 

let Clone1(dic : Dictionary<_,_>) =
    let ret = new Dictionary<_,_>()
    for KeyValue(k,v) in dic do
        ret.[k] <- v
    ret

let Clone2(dic : Dictionary<_,_>) =
    let ret = new Dictionary<_,_>()
    for kvp in dic do
        ret.[kvp.Key] <- kvp.Value 
    ret

The first uses the 'KeyValue' active pattern, and the second does things more straightforwardly. Does that help?

By on 12/17/2009 6:04 AM ()

This should also work:

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open System.Collections.Generic 

let Clone (d:Dictionary<_,_>) = new Dictionary<_,_>(d)
By on 12/18/2009 5:20 AM ()

How about:

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open System.Collections.Generic

let CloneDict (dict: Dictionary<_,_>) =
            let dict' = new Dictionary<_,_>()

            for x in dict do
                dict'.[x.Key] <- x.Value

The enumerator for the KeyValuePair is directly on the dictionary class, no need to call a method or property.

You could also consider using F#'s immutable maps if your going to be doing a lot of cloning of dicitionaries.

Cheers,
Rob

By on 12/17/2009 6:03 AM ()

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