TryElseExpression DIP

[Basile B. via Digitalmars-d]

On Monday, 5 September 2016 at 20:04:43 UTC, pineapple wrote:
> On Monday, 5 September 2016 at 19:12:02 UTC, Jacob Carlborg 
> wrote:
> [...]
>> On 2016-09-05 20:57, pineapple wrote:
> Which is easier to read and to write? Which is more 
> maintainable? Which is less prone to programmer errors? This?
>
> [...]
> This?
>
>     try{
>         do_a_thing();
>     }else{
>         depends_on_success_of_thing();
>     }
>
> Or this?
>
>     bool success = false;
>     try{
>         do_a_thing();
>         success = true;
>     }finally{
>         if(success){
>             depends_on_success_of_thing();
>         }
>     }

There's probably also a FP approach:

function TryElse(
     alias TryStatements,
     alias ElseStatements)(){}

function TryCatchElseFinally(
     alias TryStatements,
     alias ElseStatements,
     alias CatchStatements,
     alias ElseStatements,
     E : Exception = Exception)(){}

etc.

You pass delegate literals:

°°°°°°°°°°°°°°°°°°°°°
void TryElse(alias TryStatements, alias ElseStatements)()
{
     bool doElses = true;
     try TryStatements();
     catch(Throwable){}
     ElseStatements();
}

void main()
{
     int i;
     import std.conv: to;

     TryElse!(
         {i = to!int("0.42");},
         {i = -1;}
     );
}
°°°°°°°°°°°°°°°°°°°°°

With optional sugar to name each statements group:

°°°°°°°°°°°°°°°°°°°°°
template Statements(alias T)
{
     alias Statements = T;
}
alias Try = Statements;
alias Else = Statements;

void main()
{
     TryElse!(
         Try!({}),
         Else!({})
     );
}
°°°°°°°°°°°°°°°°°°°°°