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digitalmars.D - opIndexCall

reply Dan <murpsoft hotmail.com> writes:
I've recently discovered the want for an opIndexCall override in D.

For this:

struct Y {
  ...
  Y function() f;
}

struct X {
  char[][] keys;
  Y[] values;
  opIndex()
  opIndexAssign()
}

Y myF(){
  Y y;
  return y;
}


X z;

z["hello"] = &myF;

z["hello"](); // <-- can't do that.

Y function() a; // have to do this?
a = z["hello"];  // and this
a();                 // and this?
Mar 24 2007
next sibling parent Chris Nicholson-Sauls <ibisbasenji gmail.com> writes:
Dan wrote:

 I've recently discovered the want for an opIndexCall override in D.
 
 For this:
 
 struct Y {
   ...
   Y function() f;
 }
 
 struct X {
   char[][] keys;
   Y[] values;
   opIndex()
   opIndexAssign()
 }
 
 Y myF(){
   Y y;
   return y;
 }
 
 
 X z;
 
 z["hello"] = &myF;
 
 z["hello"](); // <-- can't do that.


I'm not sure, but it would help muchly to know the actual
signatures/implementations of 
opIndex and opIndexAssign.  In my own little test, this worked with no issues. 
What error 
messages were you getting?  And with what compiler version?


 Y function() a; // have to do this?
 a = z["hello"];  // and this
 a();                 // and this?


Actually, you could simplify it somewhat using auto.  But in general this
shouldn't be 
neccessary.

auto a = z["hello"];
a();

-- Chris Nicholson-Sauls
Mar 24 2007
prev sibling next sibling parent reply Bill Baxter <dnewsgroup billbaxter.com> writes:
Dan wrote:

 I've recently discovered the want for an opIndexCall override in D.
 
 For this:
 
 struct Y {
   ...
   Y function() f;
 }
 
 struct X {
   char[][] keys;
   Y[] values;
   opIndex()
   opIndexAssign()
 }
 
 Y myF(){
   Y y;
   return y;
 }
 
 
 X z;
 
 z["hello"] = &myF;
 
 z["hello"](); // <-- can't do that.
 
 Y function() a; // have to do this?
 a = z["hello"];  // and this
 a();                 // and this?


Does it work if you use a plain method instead of indexing?  I.e. if you 
add a get_elem(char[] key), does get_elem("hello")() work?

It sounds more like a bug to me than a need for an opIndexCall. 
Something seems fishy about your code, though.  You have a Y[] array, 
but no array of Y function() anywhere.

--bb
Mar 24 2007
parent reply Dan <murpsoft hotmail.com> writes:
Heh...

the code was a sample, not my actual code (obviously)  I was trying to only
show enough to represent what I was trying to suggest.

That said, I was hoping we could do:

 myAssocStruct[myCharArray](params)

Which I've never seen done before in D in any examples or source online, or in
the guide.  I haven't actually tried a minimal test case, I just didn't know
the feature existed at all and was suggesting we ought to be able to do so.

If we can, then hey... I'll try to figure it out then.  : p
Mar 24 2007
parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Dan" <murpsoft hotmail.com> wrote in message 
news:eu4man$1cs3$1 digitalmars.com...

 Heh...

 the code was a sample, not my actual code (obviously)  I was trying to 
 only show enough to represent what I was trying to suggest.

 That said, I was hoping we could do:

 myAssocStruct[myCharArray](params)

 Which I've never seen done before in D in any examples or source online, 
 or in the guide.  I haven't actually tried a minimal test case, I just 
 didn't know the feature existed at all and was suggesting we ought to be 
 able to do so.

 If we can, then hey... I'll try to figure it out then.  : p


Uhh, well:

struct FuncHolder
{
    void function(int)[char[]] funcs;

    void function(int) opIndex(char[] name)
    {
        return funcs[name];
    }

    void opIndexAssign(void function(int) func, char[] name)
    {
        funcs[name] = func;
    }
}

void foo(int x)
{
    writefln("foo: ", x);
}

void bar(int x)
{
    writefln("bar: ", x);
}

void main()
{
    FuncHolder fh;
    fh["foo"] = &foo;
    fh["bar"] = &bar;

    fh["foo"](3);
    fh["bar"](4);
}


Unless you're getting at something else?
Mar 24 2007
parent Dan <murpsoft hotmail.com> writes:
Jarrett Billingsley Wrote:


 "Dan" <murpsoft hotmail.com> wrote in message 
 news:eu4man$1cs3$1 digitalmars.com...

 Heh...

 the code was a sample, not my actual code (obviously)  I was trying to 
 only show enough to represent what I was trying to suggest.

 That said, I was hoping we could do:

 myAssocStruct[myCharArray](params)

 Which I've never seen done before in D in any examples or source online, 
 or in the guide.  I haven't actually tried a minimal test case, I just 
 didn't know the feature existed at all and was suggesting we ought to be 
 able to do so.

 If we can, then hey... I'll try to figure it out then.  : p


 
 Uhh, well:
 
 struct FuncHolder
 {
     void function(int)[char[]] funcs;
 
     void function(int) opIndex(char[] name)
     {
         return funcs[name];
     }
 
     void opIndexAssign(void function(int) func, char[] name)
     {
         funcs[name] = func;
     }
 }
 
 void foo(int x)
 {
     writefln("foo: ", x);
 }
 
 void bar(int x)
 {
     writefln("bar: ", x);
 }
 
 void main()
 {
     FuncHolder fh;
     fh["foo"] = &foo;
     fh["bar"] = &bar;
 
     fh["foo"](3);
     fh["bar"](4);
 }
 
 
 Unless you're getting at something else? 
 
 


Okay, yeah.  I wrote it out and it works.  : p

Guess there's no need for an opIndexCall then.  Maybe just perhaps having
something about this in documentation for the next guy.
Mar 25 2007
prev sibling parent Derek Parnell <derek psych.ward> writes:
On Sat, 24 Mar 2007 13:52:12 -0400, Dan wrote:


 I've recently discovered the want for an opIndexCall override in D.


It seems that all you need to do is get the return type of the opIndex
right. Here is my pretend example...

import std.stdio;
struct Y {
  Y function() f;
}

struct X {
  char[][] keys;
  Y[] values;

  // Has to return a function pointer.
  Y function() opIndex(char[] idx)
  {
     foreach(int i, char[] s; keys)
     {
         if (s == idx)
            return (values[i].f);
     }
     return null;
  }


  void opIndexAssign(Y function() fp, char[] idx)
  {
     foreach(int i, char[] s; keys)
     {
         if (s == idx)
         {
            values[i].f = fp;
            return;
         }
     }
     values.length = values.length + 1;
     (values[$-1].f) = fp;
     keys ~= idx;
  }
}

Y myF(){
  Y y;
  writefln("Got it");
  return y;
}

void main()
{
    X z;

    z["hello"] = &myF;

    z["hello"](); // <-- No worries, mate.

        Y function() a; // have to do this?
    a = z["hello"];  // and this
    a();                 // and this?
}


-- 
Derek Parnell
Melbourne, Australia
"Justice for David Hicks!"
skype: derek.j.parnell
Mar 24 2007