Create custom data types

[Ali Çehreli via Digitalmars-d-learn]

On 04/29/2015 12:53 PM, Dennis Ritchie wrote:

> On Wednesday, 29 April 2015 at 17:52:27 UTC, Ali Çehreli wrote:
>> It should be easy to make a template of it. (I really think it should
>> already be in Phobos. :) )
>
> Where can I find documentation on this subject?

Once a piece of code works for a particular type or value, it is easy to 
convert it to a template by moving the type and the value to the 
template parameter list and replace all occurrences of those with 
template parameters:

- int -> T

- -32_000 -> minValue

- 32_000 -> maxValue

Here it is:

import std.exception;

struct CustomInteger(T, T minValue, T maxValue)
{
     T value_;

     alias value this;

     @property T value() const
     {
         enforce((value_ >= minValue) &&
                 (value_ <= maxValue));

         return value_;
     }

     @property void value(T v)
     {
         value_ = v;
     }
}

unittest
{
     alias Balance = CustomInteger!(int, -32_000, 32_000);

     auto b = Balance(42);
     assert(b == 42);

     b = 40_000;

     void foo(int) {}
     assertThrown(foo(b));
}

void main()
{}

Ali