Re: extend "in" to all array types

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On Wednesday, 15 January 2014 at 15:48:13 UTC, John Colvin wrote:

On Wednesday, 15 January 2014 at 15:30:35 UTC, pplantinga wrote:

In python, I really like the ability to check if an element is in an array:

if x in array:
 # do something

D has this, but only for associative arrays. Is there any chance we could extend this to every kind of array?

import std.algorithm: canFind;

if(array.canFind(x))
    //do something


alternatively, something like this:

struct InWrapper(T)
{
    T unwrapped;
    alias unwrapped this;

    auto opBinaryRight(string op, T)(T el)
        if(op == "in")
    {
        import std.algorithm : canFind;
        return unwrapped.canFind(el);
    }
}

unittest
{
    InWrapper!(int[]) arr;
    arr = [1,2,3,4];

    assert(4 in arr);
    assert(!(5 in arr));
}

auto inWrap(T)(T[] arr)
{
    static struct InWrapper
    {
        import std.typecons: Nullable;

        private T[] payload;

        Nullable!size_t opBinaryRight(string op: "in")(T val)
        {
            Nullable!size_t index;
            foreach (i, element; payload)
            {
                if (element == val)
                {
                    index = i;
                                        
                                        return index;
                }
            }

            return index;
        }
    }

    return InWrapper(arr);
}

void main()
{
    auto arr = [0, 1, 2, 3, 4];
        auto i = 2 in arr.inWrap;
    assert(!i.isNull);
        assert(i == 2);
}