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Need help for tuple operation
f#

Dear all:

I have a question:

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let tuple1 = (0, 1)
let tuple2 = (0, 1, 2)
let tuple3 = (0, 1, 2, 3)
let tupleResult = (1, 2, 3)

I want to check if tupleResult is contained in the tuple1,

tuple2 & tuple3. The rule is like

this: for the first element in tupleRusult, here, it is 1, if it is in the

tuple1, then check the second element, it is 2, and 2 is in the tuple2, then

check the first element, which is 3, and 3 is in the tuple3. Therefore, tupleResult is contained in

tuple1, tuple2 & tuple3; if any of the 3 checks fails, then tupleResult is

NOT contained.

For example:

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let tuple1 = (0, 2)
let tuple2 = (1, 2, 3)
let tuple3 = (0, 1, 2, 3)
let tupleResult = (1, 2, 3)

Since the first element in tupleResult is 1, which is NOT

in tuple1, then tupleResult is NOT contained in tuple1, tuple2, tuple3.

Because my question has to use different length of element,

so a lot of array functions will NOT work for my issue. Tuple1, tuple2 & tuple3, each one can

have from 1 element to 4 elements; but tupleResult can have only 3 elements.

Anyone has any idea, please show me your code.

Thanks,

.

I have two questions:

1.) does the order matter (is (1,2) in (2,1))?

2.) why use tuples instead of lists or sets?

By on 7/14/2011 12:06 AM ()

Hi:
(1) The order matters, (2,1) <> (1,2)
(2) I don't know which one is better for my question, but I think since tuple can have different number of elements, so it could be a good solution. But if it is easy to solve my question using list or set, I can also use list or set.
If you have any idea, show me your code. List or set is also OK for me.
Thanks,

By on 7/14/2011 9:30 AM ()

sorry the notifications seems out of order and I've seen this just right now. Chances be that you allready got your anwers but I'll try anyhow.

As much as I understand you just want to check if a Tuple/List A is a "prefix" of Tuple/List B. As I said it's hard to do this for tuples because they are "typed by item-count" (I hope you can understand what I want to say), but if you can assume the same type for each component lists are great and easy for this (if not you can always box the items first and use obj.Equals hoping that the types overload Equals with some sense - or implement your on IEqualityComparer or whatever).

So here is my try:

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    let rec isPrefixOf a b =
        match (a,b) with
        | ([],_) -> true
        | (h::a),(h'::b) when h=h' -> isPrefixOf a b
        | _ -> false

You can test this with

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    let tests = 
        isPrefixOf [] [1;2;3],
        isPrefixOf [] [],
        isPrefixOf [1] [2;3],
        isPrefixOf [1] [1;2;3],
        isPrefixOf [1;2] [1],
        isPrefixOf [1;2] [1;2],
        isPrefixOf [1;2] [1;2;3],
        isPrefixOf [1;2] [1;3;2]
By on 7/22/2011 1:09 AM ()

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