Here is some code I wrote which enables wrapping a proxy around an object.
I am using it for my serialization library. It works in D1(1.046) and D2
(2.031)

Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.

usage: new ProxyClass!(A, cast(string)"getInt setInt getString"); would implement the methods getInt setInt and getString from A in the new class.

the code below will fail to compile but not before printing the generated code to stdout.

Shin Fujishiro has made some new templates for D2 which will make it so I
can get rid of the "setInt getInt getString" part which would make the
usage for D2: new ProxyClass!A;
which would be great!

-Rory

============================================
// author: Rory McGuire, rjmcguire@gmail.com
import std.stdio;
import std.typetuple;
import std.traits;
import std.metastrings;

//import serializer;

// this CTF from somewhere on news.digitalmars.com
string[] splitFuncs(string str) {
    string[] res;
    while (str.length > 0) {
        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
            str = str[1..$];
        }
        int to = 0;
        for (; to < str.length && str[to] != ' ' && str[to] != ','; ++to)
{}
        if (to > 0) {
            res ~= str[0..to];
            str = str[to..$];
        }
    }
    return res;
}

string MethodTypeTuple_mixin(alias a)(string[] methods) {
	string ret = "TypeTuple!("~ "typeof(&C.init."~methods[0]~")";
	foreach (method; methods[1..$]) {
		ret ~= ",typeof(&C.init."~method~")";
	}
	ret ~= ")";
	return ret;
}



// test case

class A {
	int a;
	this(int a) {
		this.a = a;
	}
	int getInt(string intname) {
		return a;
	}

	void setInt(int i) {
		a = i;
	}
	string getString(string s) {
		return s ~"1234";
	}
}


string ProxyMethods_mixin(alias C, string methodstr)() {
	string ret;
	foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
(methodstr)))) {
		// output function header
		ret ~= "\t"~ReturnType!(t).stringof ~" "~ splitFuncs
(methodstr)[i]~"(";
		// output first arg
		ret ~= ParameterTypeTuple!(t)[0].stringof~" arg";
		// output remainder of args
		foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
			ret ~= ","~t1.stringof~"
arg"~std.metastrings.ToString!(j);
		}
		// output body
		ret ~= ") {\n";
		// output serialization code
		// send method name
		ret ~= "\t\twritefln(\"serialize docall id\"); // the
method call byte id\n";
		ret ~= "\t\tbuffer ~= serialize!(string)(\""~splitFuncs
(methodstr)[i]~"\", s_state); /+ the method name +/\n";
		// send args
		ret ~= "\t\tbuffer ~= serialize!("~ ParameterTypeTuple!(t)
[0].stringof~")(arg, s_state); /+ the first argument +/\n";
		foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
			ret ~= "\t\tbuffer ~= serialize!("~ t1.stringof
~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~" +/\n";
		}
		// receive return type
		static if (!is(ReturnType!(t) == void)) {
			ret ~= "\t\treturn deserialize!("~ ReturnType!
(t).stringof ~")(buffer, des_state);\n";
		}
		ret ~= "\t}\n";
	}
	return ret;
}


class ProxyClass(alias C, string methodstr) {
		ubyte[] buffer;
		mixin(ProxyMethods_mixin!(C,methodstr)());
		pragma(msg, "class ProxyClass!("~C.stringof~", \""~
methodstr ~"\") {\n\tubyte[] buffer;\n	SerializerState s_state;\n
DeserializerState des_state;\n	this() {s_state = new SerializerState();
des_state = new DeserializerState(); }\n\n"~ ProxyMethods_mixin!
(C,methodstr)() ~"\n}\n");

}

void main() {
	auto pc = new ProxyClass!(A, cast(string)"getInt setInt
getString");
	writefln("ProxyClass: "~ pc.getString("asdf"));
}

On Wed, Aug 12, 2009 at 4:52 PM, Rory McGuire<rjmcguire@gmail.com> wrote:
> Here is some code I wrote which enables wrapping a proxy around an object.
> I am using it for my serialization library. It works in D1(1.046) and D2
> (2.031)
>
> Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.
>
> usage: new ProxyClass!(A, cast(string)"getInt setInt getString"); would
> implement the methods getInt setInt and getString from A in the new class.
>
> the code below will fail to compile but not before printing the generated code to stdout.
>
> Shin Fujishiro has made some new templates for D2 which will make it so I
> can get rid of the "setInt getInt getString" part which would make the
> usage for D2: new ProxyClass!A;
> which would be great!
>
> -Rory
>
> ============================================
> // author: Rory McGuire, rjmcguire@gmail.com
> import std.stdio;
> import std.typetuple;
> import std.traits;
> import std.metastrings;
>
> //import serializer;
>
> // this CTF from somewhere on news.digitalmars.com
> string[] splitFuncs(string str) {
>    string[] res;
>    while (str.length > 0) {
>        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
>            str = str[1..$];
>        }
>        int to = 0;
>        for (; to < str.length && str[to] != ' ' && str[to] != ','; ++to)
> {}
>        if (to > 0) {
>            res ~= str[0..to];
>            str = str[to..$];
>        }
>    }
>    return res;
> }
>
> string MethodTypeTuple_mixin(alias a)(string[] methods) {
>        string ret = "TypeTuple!("~ "typeof(&C.init."~methods[0]~")";
>        foreach (method; methods[1..$]) {
>                ret ~= ",typeof(&C.init."~method~")";
>        }
>        ret ~= ")";
>        return ret;
> }
>
>
>
> // test case
>
> class A {
>        int a;
>        this(int a) {
>                this.a = a;
>        }
>        int getInt(string intname) {
>                return a;
>        }
>
>        void setInt(int i) {
>                a = i;
>        }
>        string getString(string s) {
>                return s ~"1234";
>        }
> }
>
>
> string ProxyMethods_mixin(alias C, string methodstr)() {
>        string ret;
>        foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
> (methodstr)))) {
>                // output function header
>                ret ~= "\t"~ReturnType!(t).stringof ~" "~ splitFuncs
> (methodstr)[i]~"(";
>                // output first arg
>                ret ~= ParameterTypeTuple!(t)[0].stringof~" arg";
>                // output remainder of args
>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>                        ret ~= ","~t1.stringof~"
> arg"~std.metastrings.ToString!(j);
>                }
>                // output body
>                ret ~= ") {\n";
>                // output serialization code
>                // send method name
>                ret ~= "\t\twritefln(\"serialize docall id\"); // the
> method call byte id\n";
>                ret ~= "\t\tbuffer ~= serialize!(string)(\""~splitFuncs
> (methodstr)[i]~"\", s_state); /+ the method name +/\n";
>                // send args
>                ret ~= "\t\tbuffer ~= serialize!("~ ParameterTypeTuple!(t)
> [0].stringof~")(arg, s_state); /+ the first argument +/\n";
>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>                        ret ~= "\t\tbuffer ~= serialize!("~ t1.stringof
> ~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~" +/\n";
>                }
>                // receive return type
>                static if (!is(ReturnType!(t) == void)) {
>                        ret ~= "\t\treturn deserialize!("~ ReturnType!
> (t).stringof ~")(buffer, des_state);\n";
>                }
>                ret ~= "\t}\n";
>        }
>        return ret;
> }
>
>
> class ProxyClass(alias C, string methodstr) {
>                ubyte[] buffer;
>                mixin(ProxyMethods_mixin!(C,methodstr)());
>                pragma(msg, "class ProxyClass!("~C.stringof~", \""~
> methodstr ~"\") {\n\tubyte[] buffer;\n  SerializerState s_state;\n
> DeserializerState des_state;\n  this() {s_state = new SerializerState();
> des_state = new DeserializerState(); }\n\n"~ ProxyMethods_mixin!
> (C,methodstr)() ~"\n}\n");
>
> }
>
> void main() {
>        auto pc = new ProxyClass!(A, cast(string)"getInt setInt
> getString");
>        writefln("ProxyClass: "~ pc.getString("asdf"));
> }
>

That code is screaming for some macros.
Or variable interpolation at least.

--bb

On Wed, 12 Aug 2009 17:03:17 -0700, Bill Baxter wrote:

> On Wed, Aug 12, 2009 at 4:52 PM, Rory McGuire<rjmcguire@gmail.com> wrote:
>> Here is some code I wrote which enables wrapping a proxy around an
>> object. I am using it for my serialization library. It works in
>> D1(1.046) and D2 (2.031)
>>
>> Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.
>>
>> usage: new ProxyClass!(A, cast(string)"getInt setInt getString"); would
>> implement the methods getInt setInt and getString from A in the new
>> class.
>>
>> the code below will fail to compile but not before printing the generated code to stdout.
>>
>> Shin Fujishiro has made some new templates for D2 which will make it so
>> I can get rid of the "setInt getInt getString" part which would make
>> the usage for D2: new ProxyClass!A;
>> which would be great!
>>
>> -Rory
>>
>> ============================================ // author: Rory McGuire,
>> rjmcguire@gmail.com import std.stdio;
>> import std.typetuple;
>> import std.traits;
>> import std.metastrings;
>>
>> //import serializer;
>>
>> // this CTF from somewhere on news.digitalmars.com string[]
>> splitFuncs(string str) {
>>    string[] res;
>>    while (str.length > 0) {
>>        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
>>            str = str[1..$];
>>        }
>>        int to = 0;
>>        for (; to < str.length && str[to] != ' ' && str[to] != ',';
>>        ++to)
>> {}
>>        if (to > 0) {
>>            res ~= str[0..to];
>>            str = str[to..$];
>>        }
>>    }
>>    return res;
>> }
>>
>> string MethodTypeTuple_mixin(alias a)(string[] methods) {
>>        string ret = "TypeTuple!("~
>>        "typeof(&C.init."~methods[0]~")"; foreach (method;
>>        methods[1..$]) {
>>                ret ~= ",typeof(&C.init."~method~")";
>>        }
>>        ret ~= ")";
>>        return ret;
>> }
>>
>>
>>
>> // test case
>>
>> class A {
>>        int a;
>>        this(int a) {
>>                this.a = a;
>>        }
>>        int getInt(string intname) {
>>                return a;
>>        }
>>
>>        void setInt(int i) {
>>                a = i;
>>        }
>>        string getString(string s) {
>>                return s ~"1234";
>>        }
>> }
>>
>>
>> string ProxyMethods_mixin(alias C, string methodstr)() {
>>        string ret;
>>        foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
>> (methodstr)))) {
>>                // output function header
>>                ret ~= "\t"~ReturnType!(t).stringof ~" "~
>>                splitFuncs
>> (methodstr)[i]~"(";
>>                // output first arg
>>                ret ~= ParameterTypeTuple!(t)[0].stringof~"
>>                arg"; // output remainder of args
>>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>>                        ret ~= ","~t1.stringof~"
>> arg"~std.metastrings.ToString!(j);
>>                }
>>                // output body
>>                ret ~= ") {\n";
>>                // output serialization code
>>                // send method name
>>                ret ~= "\t\twritefln(\"serialize docall id\");
>>                // the
>> method call byte id\n";
>>                ret ~= "\t\tbuffer ~=
>>                serialize!(string)(\""~splitFuncs
>> (methodstr)[i]~"\", s_state); /+ the method name +/\n";
>>                // send args
>>                ret ~= "\t\tbuffer ~= serialize!("~
>>                ParameterTypeTuple!(t)
>> [0].stringof~")(arg, s_state); /+ the first argument +/\n";
>>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>>                        ret ~= "\t\tbuffer ~= serialize!("~
>>                        t1.stringof
>> ~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~" +/\n";
>>                }
>>                // receive return type
>>                static if (!is(ReturnType!(t) == void)) {
>>                        ret ~= "\t\treturn deserialize!("~
>>                        ReturnType!
>> (t).stringof ~")(buffer, des_state);\n";
>>                }
>>                ret ~= "\t}\n";
>>        }
>>        return ret;
>> }
>>
>>
>> class ProxyClass(alias C, string methodstr) {
>>                ubyte[] buffer;
>>                mixin(ProxyMethods_mixin!(C,methodstr)());
>>                pragma(msg, "class ProxyClass!("~C.stringof~",
>>                \""~
>> methodstr ~"\") {\n\tubyte[] buffer;\n  SerializerState s_state;\n
>> DeserializerState des_state;\n  this() {s_state = new
>> SerializerState(); des_state = new DeserializerState(); }\n\n"~
>> ProxyMethods_mixin! (C,methodstr)() ~"\n}\n");
>>
>> }
>>
>> void main() {
>>        auto pc = new ProxyClass!(A, cast(string)"getInt setInt
>> getString");
>>        writefln("ProxyClass: "~ pc.getString("asdf"));
>> }
>>
>>
> That code is screaming for some macros. Or variable interpolation at least.
> 
> --bb

Where would you propose that one would use 'macro'?

On Thu, Aug 13, 2009 at 12:43 AM, Rory McGuire<rjmcguire@gmail.com> wrote:
> On Wed, 12 Aug 2009 17:03:17 -0700, Bill Baxter wrote:
>
>> On Wed, Aug 12, 2009 at 4:52 PM, Rory McGuire<rjmcguire@gmail.com> wrote:
>>> Here is some code I wrote which enables wrapping a proxy around an
>>> object. I am using it for my serialization library. It works in
>>> D1(1.046) and D2 (2.031)
>>>
>>> Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.
>>>
>>> usage: new ProxyClass!(A, cast(string)"getInt setInt getString"); would
>>> implement the methods getInt setInt and getString from A in the new
>>> class.
>>>
>>> the code below will fail to compile but not before printing the generated code to stdout.
>>>
>>> Shin Fujishiro has made some new templates for D2 which will make it so
>>> I can get rid of the "setInt getInt getString" part which would make
>>> the usage for D2: new ProxyClass!A;
>>> which would be great!
>>>
>>> -Rory
>>>
>>> ============================================ // author: Rory McGuire,
>>> rjmcguire@gmail.com import std.stdio;
>>> import std.typetuple;
>>> import std.traits;
>>> import std.metastrings;
>>>
>>> //import serializer;
>>>
>>> // this CTF from somewhere on news.digitalmars.com string[]
>>> splitFuncs(string str) {
>>>    string[] res;
>>>    while (str.length > 0) {
>>>        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
>>>            str = str[1..$];
>>>        }
>>>        int to = 0;
>>>        for (; to < str.length && str[to] != ' ' && str[to] != ',';
>>>        ++to)
>>> {}
>>>        if (to > 0) {
>>>            res ~= str[0..to];
>>>            str = str[to..$];
>>>        }
>>>    }
>>>    return res;
>>> }
>>>
>>> string MethodTypeTuple_mixin(alias a)(string[] methods) {
>>>        string ret = "TypeTuple!("~
>>>        "typeof(&C.init."~methods[0]~")"; foreach (method;
>>>        methods[1..$]) {
>>>                ret ~= ",typeof(&C.init."~method~")";
>>>        }
>>>        ret ~= ")";
>>>        return ret;
>>> }
>>>
>>>
>>>
>>> // test case
>>>
>>> class A {
>>>        int a;
>>>        this(int a) {
>>>                this.a = a;
>>>        }
>>>        int getInt(string intname) {
>>>                return a;
>>>        }
>>>
>>>        void setInt(int i) {
>>>                a = i;
>>>        }
>>>        string getString(string s) {
>>>                return s ~"1234";
>>>        }
>>> }
>>>
>>>
>>> string ProxyMethods_mixin(alias C, string methodstr)() {
>>>        string ret;
>>>        foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
>>> (methodstr)))) {
>>>                // output function header
>>>                ret ~= "\t"~ReturnType!(t).stringof ~" "~
>>>                splitFuncs
>>> (methodstr)[i]~"(";
>>>                // output first arg
>>>                ret ~= ParameterTypeTuple!(t)[0].stringof~"
>>>                arg"; // output remainder of args
>>>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>>>                        ret ~= ","~t1.stringof~"
>>> arg"~std.metastrings.ToString!(j);
>>>                }
>>>                // output body
>>>                ret ~= ") {\n";
>>>                // output serialization code
>>>                // send method name
>>>                ret ~= "\t\twritefln(\"serialize docall id\");
>>>                // the
>>> method call byte id\n";
>>>                ret ~= "\t\tbuffer ~=
>>>                serialize!(string)(\""~splitFuncs
>>> (methodstr)[i]~"\", s_state); /+ the method name +/\n";
>>>                // send args
>>>                ret ~= "\t\tbuffer ~= serialize!("~
>>>                ParameterTypeTuple!(t)
>>> [0].stringof~")(arg, s_state); /+ the first argument +/\n";
>>>                foreach (j, t1; ParameterTypeTuple!(t)[1..$]) {
>>>                        ret ~= "\t\tbuffer ~= serialize!("~
>>>                        t1.stringof
>>> ~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~" +/\n";
>>>                }
>>>                // receive return type
>>>                static if (!is(ReturnType!(t) == void)) {
>>>                        ret ~= "\t\treturn deserialize!("~
>>>                        ReturnType!
>>> (t).stringof ~")(buffer, des_state);\n";
>>>                }
>>>                ret ~= "\t}\n";
>>>        }
>>>        return ret;
>>> }
>>>
>>>
>>> class ProxyClass(alias C, string methodstr) {
>>>                ubyte[] buffer;
>>>                mixin(ProxyMethods_mixin!(C,methodstr)());
>>>                pragma(msg, "class ProxyClass!("~C.stringof~",
>>>                \""~
>>> methodstr ~"\") {\n\tubyte[] buffer;\n  SerializerState s_state;\n
>>> DeserializerState des_state;\n  this() {s_state = new
>>> SerializerState(); des_state = new DeserializerState(); }\n\n"~
>>> ProxyMethods_mixin! (C,methodstr)() ~"\n}\n");
>>>
>>> }
>>>
>>> void main() {
>>>        auto pc = new ProxyClass!(A, cast(string)"getInt setInt
>>> getString");
>>>        writefln("ProxyClass: "~ pc.getString("asdf"));
>>> }
>>>
>>>
>> That code is screaming for some macros. Or variable interpolation at least.
>>
>> --bb
>
> Where would you propose that one would use 'macro'?
>

It doesn't exist yet, so there's not much you can do about it. Unfortunately code that generates code in D pretty much has to look like what you wrote there.  I'm just saying it's not a lot of fun to read such code.  Compare with Lisp macros that are almost as readable as regular Lisp functions.

Or maybe instead of macros, what's needed is variable interpolation like Perl has.  Meaning you can embed a variable inside a string. (e.g. http://www.perlmeme.org/howtos/using_perl/interpolation.html) If one could write something like

    ret ~= "\t$ReturnType!(t).stringof splitFuncs(methodstr)[i]("

It would at least look a bit nicer than

     ret ~= "\t"~ReturnType!(t).stringof ~" "~splitFuncs(methodstr)[i]~"(";

with all the ~" "~ everywhere.

--bb

Bill Baxter wrote:
> On Thu, Aug 13, 2009 at 12:43 AM, Rory McGuire<rjmcguire@gmail.com> wrote:
>> On Wed, 12 Aug 2009 17:03:17 -0700, Bill Baxter wrote:
>>
>>> On Wed, Aug 12, 2009 at 4:52 PM, Rory McGuire<rjmcguire@gmail.com> wrote:
>>>> Here is some code I wrote which enables wrapping a proxy around an
>>>> object. I am using it for my serialization library. It works in
>>>> D1(1.046) and D2 (2.031)
>>>>
>>>> Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.
>>>>
>>>> usage: new ProxyClass!(A, cast(string)"getInt setInt getString"); would
>>>> implement the methods getInt setInt and getString from A in the new
>>>> class.
>>>>
>>>> the code below will fail to compile but not before printing the generated code to stdout.
>>>>
>>>> Shin Fujishiro has made some new templates for D2 which will make it so
>>>> I can get rid of the "setInt getInt getString" part which would make
>>>> the usage for D2: new ProxyClass!A;
>>>> which would be great!
>>>>
>>>> -Rory
>>>>
>>>> ============================================ // author: Rory McGuire,
>>>> rjmcguire@gmail.com import std.stdio;
>>>> import std.typetuple;
>>>> import std.traits;
>>>> import std.metastrings;
>>>>
>>>> //import serializer;
>>>>
>>>> // this CTF from somewhere on news.digitalmars.com string[]
>>>> splitFuncs(string str) {
>>>>    string[] res;
>>>>    while (str.length > 0) {
>>>>        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
>>>>            str = str[1..$];
>>>>        }
>>>>        int to = 0;
>>>>        for (; to < str.length && str[to] != ' ' && str[to] != ',';
>>>>        ++to)
>>>> {}
>>>>        if (to > 0) {
>>>>            res ~= str[0..to];
>>>>            str = str[to..$];
>>>>        }
>>>>    }
>>>>    return res;
>>>> }
>>>>
>>>> string MethodTypeTuple_mixin(alias a)(string[] methods) {
>>>>        string ret = "TypeTuple!("~
>>>>        "typeof(&C.init."~methods[0]~")"; foreach (method;
>>>>        methods[1..$]) {
>>>>                ret ~= ",typeof(&C.init."~method~")";
>>>>        }
>>>>        ret ~= ")";
>>>>        return ret;
>>>> }
>>>>
>>>>
>>>>
>>>> // test case
>>>>
>>>> class A {
>>>>        int a;
>>>>        this(int a) {
>>>>                this.a = a;
>>>>        }
>>>>        int getInt(string intname) {
>>>>                return a;
>>>>        }
>>>>
>>>>        void setInt(int i) {
>>>>                a = i;
>>>>        }
>>>>        string getString(string s) {
>>>>                return s ~"1234";
>>>>        }
>>>> }
>>>>
>>>>
>>>> string ProxyMethods_mixin(alias C, string methodstr)() {
>>>>        string ret;
>>>>        foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
>>>> (methodstr)))) {
>>>>                // output function header
>>>>                ret ~= "\t"~ReturnType!(t).stringof ~" "~
>>>>                splitFuncs
>>>> (methodstr)[i]~"(";
>>>>                // output first arg
>>>>                ret ~= ParameterTypeTuple!(t)[0].stringof~"
>>>>                arg"; // output remainder of args
>>>>                foreach (j, t1; ParameterTypeTuple!(t)[1...$]) {
>>>>                        ret ~= ","~t1.stringof~"
>>>> arg"~std.metastrings.ToString!(j);
>>>>                }
>>>>                // output body
>>>>                ret ~= ") {\n";
>>>>                // output serialization code
>>>>                // send method name
>>>>                ret ~= "\t\twritefln(\"serialize docall id\");
>>>>                // the
>>>> method call byte id\n";
>>>>                ret ~= "\t\tbuffer ~=
>>>>                serialize!(string)(\""~splitFuncs
>>>> (methodstr)[i]~"\", s_state); /+ the method name +/\n";
>>>>                // send args
>>>>                ret ~= "\t\tbuffer ~= serialize!("~
>>>>                ParameterTypeTuple!(t)
>>>> [0].stringof~")(arg, s_state); /+ the first argument +/\n";
>>>>                foreach (j, t1; ParameterTypeTuple!(t)[1...$]) {
>>>>                        ret ~= "\t\tbuffer ~= serialize!("~
>>>>                        t1.stringof
>>>> ~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~" +/\n";
>>>>                }
>>>>                // receive return type
>>>>                static if (!is(ReturnType!(t) == void)) {
>>>>                        ret ~= "\t\treturn deserialize!("~
>>>>                        ReturnType!
>>>> (t).stringof ~")(buffer, des_state);\n";
>>>>                }
>>>>                ret ~= "\t}\n";
>>>>        }
>>>>        return ret;
>>>> }
>>>>
>>>>
>>>> class ProxyClass(alias C, string methodstr) {
>>>>                ubyte[] buffer;
>>>>                mixin(ProxyMethods_mixin!(C,methodstr)());
>>>>                pragma(msg, "class ProxyClass!("~C.stringof~",
>>>>                \""~
>>>> methodstr ~"\") {\n\tubyte[] buffer;\n  SerializerState s_state;\n
>>>> DeserializerState des_state;\n  this() {s_state = new
>>>> SerializerState(); des_state = new DeserializerState(); }\n\n"~
>>>> ProxyMethods_mixin! (C,methodstr)() ~"\n}\n");
>>>>
>>>> }
>>>>
>>>> void main() {
>>>>        auto pc = new ProxyClass!(A, cast(string)"getInt setInt
>>>> getString");
>>>>        writefln("ProxyClass: "~ pc.getString("asdf"));
>>>> }
>>>>
>>>>
>>> That code is screaming for some macros. Or variable interpolation at least.
>>>
>>> --bb
>> Where would you propose that one would use 'macro'?
>>
> 
> It doesn't exist yet, so there's not much you can do about it. Unfortunately code that generates code in D pretty much has to look like what you wrote there.  I'm just saying it's not a lot of fun to read such code.  Compare with Lisp macros that are almost as readable as regular Lisp functions.
> 
> Or maybe instead of macros, what's needed is variable interpolation like Perl has.  Meaning you can embed a variable inside a string. (e.g. http://www.perlmeme.org/howtos/using_perl/interpolation.html) If one could write something like
> 
>     ret ~= "\t$ReturnType!(t).stringof splitFuncs(methodstr)[i]("
> 
> It would at least look a bit nicer than
> 
>      ret ~= "\t"~ReturnType!(t).stringof ~" "~splitFuncs(methodstr)[i]~"(";
> 
> with all the ~" "~ everywhere.
> 
> --bb

I did a blog post about that.

http://while-nan.blogspot.com/2007/06/mixins-ctfe-and-shell-style-variable.html

For reference, you could (with a few modifications) make it look like this:

mixin(ctsub(`
   ret ~= "\t${ReturnType!(t).stringof} splitFuncs(methodstr)[i]("
`));

Not perfect, but perhaps slightly more readable.  I don't remember how robust the parsing logic was, though.

On Fri, 14 Aug 2009 00:16:39 +1000, Daniel Keep wrote:

> Bill Baxter wrote:
>> On Thu, Aug 13, 2009 at 12:43 AM, Rory McGuire<rjmcguire@gmail.com> wrote:
>>> On Wed, 12 Aug 2009 17:03:17 -0700, Bill Baxter wrote:
>>>
>>>> On Wed, Aug 12, 2009 at 4:52 PM, Rory McGuire<rjmcguire@gmail.com> wrote:
>>>>> Here is some code I wrote which enables wrapping a proxy around an
>>>>> object. I am using it for my serialization library. It works in
>>>>> D1(1.046) and D2 (2.031)
>>>>>
>>>>> Posting it here for reference by all before I add to much of the stuff specific to my use, should make it easier to follow.
>>>>>
>>>>> usage: new ProxyClass!(A, cast(string)"getInt setInt getString");
>>>>> would implement the methods getInt setInt and getString from A in
>>>>> the new class.
>>>>>
>>>>> the code below will fail to compile but not before printing the generated code to stdout.
>>>>>
>>>>> Shin Fujishiro has made some new templates for D2 which will make it
>>>>> so I can get rid of the "setInt getInt getString" part which would
>>>>> make the usage for D2: new ProxyClass!A;
>>>>> which would be great!
>>>>>
>>>>> -Rory
>>>>>
>>>>> ============================================ // author: Rory
>>>>> McGuire, rjmcguire@gmail.com import std.stdio; import std.typetuple;
>>>>> import std.traits;
>>>>> import std.metastrings;
>>>>>
>>>>> //import serializer;
>>>>>
>>>>> // this CTF from somewhere on news.digitalmars.com string[]
>>>>> splitFuncs(string str) {
>>>>>    string[] res;
>>>>>    while (str.length > 0) {
>>>>>        while (str.length > 0 && (' ' == str[0] || ',' == str[0])) {
>>>>>            str = str[1..$];
>>>>>        }
>>>>>        int to = 0;
>>>>>        for (; to < str.length && str[to] != ' ' && str[to] != ',';
>>>>>        ++to)
>>>>> {}
>>>>>        if (to > 0) {
>>>>>            res ~= str[0..to];
>>>>>            str = str[to..$];
>>>>>        }
>>>>>    }
>>>>>    return res;
>>>>> }
>>>>>
>>>>> string MethodTypeTuple_mixin(alias a)(string[] methods) {
>>>>>        string ret = "TypeTuple!("~
>>>>>        "typeof(&C.init."~methods[0]~")"; foreach (method;
>>>>>        methods[1..$]) {
>>>>>                ret ~= ",typeof(&C.init."~method~")";
>>>>>        }
>>>>>        ret ~= ")";
>>>>>        return ret;
>>>>> }
>>>>>
>>>>>
>>>>>
>>>>> // test case
>>>>>
>>>>> class A {
>>>>>        int a;
>>>>>        this(int a) {
>>>>>                this.a = a;
>>>>>        }
>>>>>        int getInt(string intname) {
>>>>>                return a;
>>>>>        }
>>>>>
>>>>>        void setInt(int i) {
>>>>>                a = i;
>>>>>        }
>>>>>        string getString(string s) {
>>>>>                return s ~"1234";
>>>>>        }
>>>>> }
>>>>>
>>>>>
>>>>> string ProxyMethods_mixin(alias C, string methodstr)() {
>>>>>        string ret;
>>>>>        foreach(i, t; mixin(MethodTypeTuple_mixin!(C)(splitFuncs
>>>>> (methodstr)))) {
>>>>>                // output function header
>>>>>                ret ~= "\t"~ReturnType!(t).stringof ~" "~ splitFuncs
>>>>> (methodstr)[i]~"(";
>>>>>                // output first arg
>>>>>                ret ~= ParameterTypeTuple!(t)[0].stringof~" arg"; //
>>>>>                output remainder of args
>>>>>                foreach (j, t1; ParameterTypeTuple!(t)[1...$]) {
>>>>>                        ret ~= ","~t1.stringof~"
>>>>> arg"~std.metastrings.ToString!(j);
>>>>>                }
>>>>>                // output body
>>>>>                ret ~= ") {\n";
>>>>>                // output serialization code
>>>>>                // send method name
>>>>>                ret ~= "\t\twritefln(\"serialize docall id\"); // the
>>>>> method call byte id\n";
>>>>>                ret ~= "\t\tbuffer ~=
>>>>>                serialize!(string)(\""~splitFuncs
>>>>> (methodstr)[i]~"\", s_state); /+ the method name +/\n";
>>>>>                // send args
>>>>>                ret ~= "\t\tbuffer ~= serialize!("~
>>>>>                ParameterTypeTuple!(t)
>>>>> [0].stringof~")(arg, s_state); /+ the first argument +/\n";
>>>>>                foreach (j, t1; ParameterTypeTuple!(t)[1...$]) {
>>>>>                        ret ~= "\t\tbuffer ~= serialize!("~
>>>>>                        t1.stringof
>>>>> ~")(arg"~ToString!(j)~", s_state); /+ argument "~ToString!(j)~"
>>>>> +/\n";
>>>>>                }
>>>>>                // receive return type
>>>>>                static if (!is(ReturnType!(t) == void)) {
>>>>>                        ret ~= "\t\treturn deserialize!("~
>>>>>                        ReturnType!
>>>>> (t).stringof ~")(buffer, des_state);\n";
>>>>>                }
>>>>>                ret ~= "\t}\n";
>>>>>        }
>>>>>        return ret;
>>>>> }
>>>>>
>>>>>
>>>>> class ProxyClass(alias C, string methodstr) {
>>>>>                ubyte[] buffer;
>>>>>                mixin(ProxyMethods_mixin!(C,methodstr)());
>>>>>                pragma(msg, "class ProxyClass!("~C.stringof~", \""~
>>>>> methodstr ~"\") {\n\tubyte[] buffer;\n  SerializerState s_state;\n
>>>>> DeserializerState des_state;\n  this() {s_state = new
>>>>> SerializerState(); des_state = new DeserializerState(); }\n\n"~
>>>>> ProxyMethods_mixin! (C,methodstr)() ~"\n}\n");
>>>>>
>>>>> }
>>>>>
>>>>> void main() {
>>>>>        auto pc = new ProxyClass!(A, cast(string)"getInt setInt
>>>>> getString");
>>>>>        writefln("ProxyClass: "~ pc.getString("asdf"));
>>>>> }
>>>>>
>>>>>
>>>> That code is screaming for some macros. Or variable interpolation at least.
>>>>
>>>> --bb
>>> Where would you propose that one would use 'macro'?
>>>
>>>
>> It doesn't exist yet, so there's not much you can do about it. Unfortunately code that generates code in D pretty much has to look like what you wrote there.  I'm just saying it's not a lot of fun to read such code.  Compare with Lisp macros that are almost as readable as regular Lisp functions.
>> 
>> Or maybe instead of macros, what's needed is variable interpolation like Perl has.  Meaning you can embed a variable inside a string. (e.g. http://www.perlmeme.org/howtos/using_perl/interpolation.html) If one could write something like
>> 
>>     ret ~= "\t$ReturnType!(t).stringof splitFuncs(methodstr)[i]("
>> 
>> It would at least look a bit nicer than
>> 
>>      ret ~= "\t"~ReturnType!(t).stringof ~"
>>      "~splitFuncs(methodstr)[i]~"(";
>> 
>> with all the ~" "~ everywhere.
>> 
>> --bb
> 
> I did a blog post about that.
> 
> http://while-nan.blogspot.com/2007/06/mixins-ctfe-and-shell-style-
variable.html
> 
> For reference, you could (with a few modifications) make it look like
> this:
> 
> mixin(ctsub(`
>    ret ~= "\t${ReturnType!(t).stringof} splitFuncs(methodstr)[i]("
> `));
> 
> Not perfect, but perhaps slightly more readable.  I don't remember how robust the parsing logic was, though.

hm, that does look neater. I might use that.

main reason I posted though was because I couldn't find anything about how to do this sort of thing in D that was straight forward, the code as I posted it should hopefully be easy for people learning D ctfe programming. ~= is easy to understand, and keeps the code small, only relying on the standard library.

Thanks
Rory

Bill Baxter:
>     ret ~= "\t$ReturnType!(t).stringof splitFuncs(methodstr)[i]("
> It would at least look a bit nicer than
>      ret ~= "\t"~ReturnType!(t).stringof ~" "~splitFuncs(methodstr)[i]~"(";
> with all the ~" "~ everywhere.

Currently you can do (I think it doesn't work well in D2 now):
import std.metastrings: Format;
...
ret ~= Format!("\t %s %s(", ReturnType!(t).stringof, splitFuncs(methodstr)[i]);

Bye,
bearophile