Re: C++ to D

[Ali Çehreli via Digitalmars-d-learn]

On 03/11/2015 07:33 AM, Dennis Ritchie wrote:

How to rewrite this in D to the handler method for the input parameter
was determined on average in O(1)?

D's associative arrays are hash tables.

The following program is as similar to the C++ one as possible:

import std.stdio;
import std.range;

class A
{
public:
    alias Func = void delegate(A, string);
    static const Func[string] handlers;

    static this()
    {
        handlers = [ "first" : (A a, string b) => a.foo1(b),
                     "second" : (A a, string b) => a.foo2(b),
                     "third" : (A a, string b) => a.foo3(b) ];
    }

    void foo(string s)
    {
        const handler = s in handlers;
        if (handler) {
            (*handler)(this, s);
        }

        m_buf ~= s ~ ' ';
    }

protected:
    void foo1(string s)
    {
        writeln(s);
    }

    void foo2(string s)
    {
        writeln(s.retro);
    }

    void foo3(string s)
    {
        writefln("%s, %s", s, m_buf);
    }

    string m_buf;
}

void main()
{
    auto a = new A();
    a.foo("first");
    a.foo("second");
    a.foo("third");
}

Ali