Re: D idom for removing array elements

[cym13 via Digitalmars-d-learn]

On Saturday, 28 January 2017 at 10:46:29 UTC, albert-j wrote:

On Friday, 27 January 2017 at 08:15:56 UTC, Dukc wrote:

void main()

{ import std.stdio, std.algorithm, std.range, std.array, std.datetime;

    int[] a = [1, 2, 3, 4, 5, 6, 7, 4].cycle.take(2000).array;
    int[] b = [3, 4, 6].cycle.take(2000).array;

    void originalMethod()
    {   auto c = a.remove!(x => b.canFind(x));
        assert(c[0 .. 4] == [1, 2, 5, 7]);
    }

    void WilsonMethod()
    {   auto c = a.filter!(x => !b.canFind(x)).array;
        assert(c[0 .. 4] == [1, 2, 5, 7]);
    }

    void myMethod()
    {   auto sortedB = sort(b.dup);
        auto c = a
        .   filter!(i => !sortedB.contains(i))
        .   array
        ;
        assert(c[0 .. 4] == [1, 2, 5, 7]);
    }

auto r = benchmark!(originalMethod, WilsonMethod, myMethod)(1);

    foreach(result; r) result.writeln;
}

How to make it work with std.container.array?

Here is an example:

import std.container.array;
alias ArrI = Array!int;

auto removeAll(ArrI a, ArrI b) {
    import std.array;
    import std.range;
    import std.algorithm;

    auto sortedB = sort(b[]).uniq.array;
    auto c = a[].partition!(v => sortedB.assumeSorted.contains(v),
                          SwapStrategy.stable);
    return ArrI(c);
}

void main() {
    import std.stdio;

    auto a = ArrI(1, 2, 3, 4, 5, 6, 7, 4);
    auto b = ArrI(3, 4, 6);

    a.removeAll(b)[].writeln;
}

Note especially how you slice an Array to access its data.