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How to count number of times item is found in a list
f#functionalpython

I'm trying to learn F# (and functional languages) and I came across an article "How to Write a Spelling Corrector" which has an example in python that I'm trying to convert in F#.
In python the function is:

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def train(features):
    model = collections.defaultdict(lambda: 1)
    for f in features:
        model[f] += 1
    return model

Basically it counts how many times each word is found in the features collection and store the result in the model collection.

.

take a look at Seq.countBy as documented in:

[link:research.microsoft.com]

sample code:

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> > let wordList = ["three";"two";"one";"three";"two";"three"];;
val wordList : string list

> wordList |> Seq.countBy (fun x -> x);;
val it : seq<string * int> = seq [("three", 3); ("two", 2); ("one", 1)]

hope this helps

By on 3/2/2008 8:29 PM ()

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