Hi dlang community,

I'm trying to implement a "reset" functionality which should revert all variables to the program start initial state.

Example:

import Graph;
protected Edge[string] m_string2edge;

int main()
{
    // adding some elements
    // not important how it works
    // m_string2edge[name] = e;

    // resetting it
    m_string2edge = null;
    m_string2edge = new Edge[string]; // <- won't compile

    return 0;
}

How do I revert my variable to the init state?

Thanks in advance,
Simon

On Thursday, 30 January 2020 at 21:09:41 UTC, Simon wrote:
> Hi dlang community,
>
> I'm trying to implement a "reset" functionality which should revert all variables to the program start initial state.
>
> Example:
>
> import Graph;
> protected Edge[string] m_string2edge;
>
> int main()
> {
>     // adding some elements
>     // not important how it works
>     // m_string2edge[name] = e;
>
>     // resetting it
>     m_string2edge = null;
>     m_string2edge = new Edge[string]; // <- won't compile
>
>     return 0;
> }
>
> How do I revert my variable to the init state?
>
> Thanks in advance,
> Simon

You can use m_string2edge.clear() if you want to remove all entries from m_string2edge.

See https://dlang.org/spec/hash-map.html#properties

On Thursday, 30 January 2020 at 21:09:41 UTC, Simon wrote:
> How do I revert my variable to the init state?

null is the initial state for those.

On Thursday, 30 January 2020 at 21:36:53 UTC, Adam D. Ruppe wrote:
> On Thursday, 30 January 2020 at 21:09:41 UTC, Simon wrote:
>> How do I revert my variable to the init state?
>
> null is the initial state for those.

More generally, .init can be used as to get the initial state for any type.

ie.
  m_string2edge = typeof(m_string2edge).init;

On Thursday, 30 January 2020 at 21:18:04 UTC, MoonlightSentinel wrote:
> On Thursday, 30 January 2020 at 21:09:41 UTC, Simon wrote:
>> Hi dlang community,
>>
>> I'm trying to implement a "reset" functionality which should revert all variables to the program start initial state.
>>
>> Example:
>>
>> import Graph;
>> protected Edge[string] m_string2edge;
>>
>> int main()
>> {
>>     // adding some elements
>>     // not important how it works
>>     // m_string2edge[name] = e;
>>
>>     // resetting it
>>     m_string2edge = null;
>>     m_string2edge = new Edge[string]; // <- won't compile
>>
>>     return 0;
>> }
>>
>> How do I revert my variable to the init state?
>>
>> Thanks in advance,
>> Simon
>
> You can use m_string2edge.clear() if you want to remove all entries from m_string2edge.
>
> See https://dlang.org/spec/hash-map.html#properties

Hi MoonlightSentinel,

in this case it won't compile:
..\Electrics.d(42): Error: function Electrics.clear() is not callable using argument types (Edge[string])
..\Electrics.d(42):        expected 0 argument(s), not 1

On Friday, 31 January 2020 at 14:01:04 UTC, Minty Fresh wrote:
> On Thursday, 30 January 2020 at 21:36:53 UTC, Adam D. Ruppe wrote:
>> On Thursday, 30 January 2020 at 21:09:41 UTC, Simon wrote:
>>> How do I revert my variable to the init state?
>>
>> null is the initial state for those.
>
> More generally, .init can be used as to get the initial state for any type.
>
> ie.
>   m_string2edge = typeof(m_string2edge).init;

Thank you, Minty Fresh, this was the solution!