nested enum like template generator

[Ali Çehreli]

On 07/16/2013 01:40 PM, JS wrote:

 > The problem is I can't declare my "global" int variables directly inside
 > the template. This does make it hard to use the same variable across
 > multiple functions...
 >
 > template A
 > {
 >      int c; // makes c near useless, can't use it like a normal it...
 > }

Could you please provide complete code. The following works:

import std.stdio;
import std.conv;

template A()
{
     int c;
}

string func(T)()
{
     string result;

     alias counter = A!().c;

     for ( ; counter < 10; ++counter) {
         result ~= counter.to!string;
     }

     return result;
}

void main()
{
     writeln(func!int());
}

Prints:

0123456789

This works as well:

import std.stdio;
import std.conv;

template A()
{
     int c;

     string func()
     {
         string result;

         for ( ; c < 10; ++c) {
             result ~= c.to!string;
         }

         return result;
     }
}

void main()
{
     writeln(A!().func());
}

Prints the same:

0123456789

 > the error message given obfuscates the reason.

What is the error message?

 > Unfortunately it requires a messy technique to get around by using nested
 > functions. (The parent function holds the global state of the child
 > functions)

Well, this works as well:

import std.stdio;
import std.conv;

template A()
{
     int c;

     string globalFunc()
     {
         string result;

         void func()
         {
             for ( ; c < 10; ++c) {
                 result ~= c.to!string;
             }
         }

         func();
         return result;
     }
}

void main()
{
     writeln(A!().globalFunc());
}

Again, prints the same:

0123456789

 > It would be nice if we had some way to data globally(in module).
 >
 > e.g., __ctfestore["name"] = value;

I would expect model-level objects start their lives after the program 
starts running but their initial value can be calculated during compile 
time:

import std.stdio;
import std.conv;

int[string] ctfestore;

static this()
{
     ctfestore = A!().globalFunc();
}

template A()
{
     int c;

     int[string] globalFunc()
     {
         int[string] result;

         void func()
         {
             for ( ; c < 10; ++c) {
                 result[c.to!string] = c;
             }
         }

         func();
         return result;
     }
}

void main()
{
     writeln(ctfestore);
}

Prints:

["0":0, "4":4, "8":8, "1":1, "5":5, "9":9, "2":2, "6":6, "3":3, "7":7]

Ali