Re: More uses of operator "in"

[Baz via Digitalmars-d-learn]

On Tuesday, 28 October 2014 at 13:50:24 UTC, Nordlöw wrote:
Has there been any proposals/plans to make operator "in" work 
for elements in ranges such as

    assert('x' in ['x']);

I'm missing that Python feature when I work in D.

There is also something similar in Pascal, at the language level. 
Very handy when working with characters or enums.

I think in D it's possible to create some library types which 
allow an almost similar syntax. For example this one, briefly 
written after reading your post:

----
import std.stdio;

// global variable to get rid of 
https://issues.dlang.org/show_bug.cgi?id=11877
CharSet charSet;
struct CharSet
{
    private string str;
    public:
        typeof(this) opSlice(char lo, char hi)
        {
            CharSet result;
            foreach(c; lo .. hi)
                result.str ~= c;
            return result;
        }
        typeof(this) opSlice(char lohi)
        {
            CharSet result;
            result.str ~= lohi;
            return result;
        }
        bool opIn_r(char elem)
        {
            if (str == "")
                return false;
            else
                return ((elem >= str[0]) & (elem <= str[$-1]));
        }
        string toString()
        {
            return str;
        }
}

void main(string args[])
{
    auto a2k = charSet['a' .. 'k'+1];
    auto A2K = charSet['A' .. 'K'+1];
    auto Z29 = charSet['0' .. '9'+1];

    assert( 'a' in a2k );
    assert( !('x' in a2k) );

    assert( 'A' in A2K );
    assert( !('X' in A2K) );

    import std.conv;
    assert( to!string(Z29) == "0123456789" );

    assert( 'x' in charSet['x'..'x'+1] );
}
----