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digitalmars.D.learn - "if" statement

reply Francesco Mecca <me francescomecca.eu> writes:
https://run.dlang.io/is/zRcj59

```
alias Alg = Algebraic!(int, string);

void main()
{
	int n = 2;
     Alg value;

     value = n == 2 ? 2 : "string";
}
```

The original code used SumType but the effect is the same.

I suppose that I could write the following:

```
     if(n == 2) value = 2;
     else value = "string";
```

Is there a workaround for this that maintains a similar syntactic 
structure?
is this behaviour accepted or should the compiler translate the 
first case in the second?
Mar 24
next sibling parent ag0aep6g <anonymous example.com> writes:
On 24.03.19 13:45, Francesco Mecca wrote:
 ```
 alias Alg = Algebraic!(int, string);
 
 void main()
 {
      int n = 2;
      Alg value;
 
      value = n == 2 ? 2 : "string";
 }
 ```
 
 The original code used SumType but the effect is the same.
 
 I suppose that I could write the following:
 
 ```
      if(n == 2) value = 2;
      else value = "string";
 ```
 
 Is there a workaround for this that maintains a similar syntactic 
 structure?
value = n == 2 ? Alg(2) : Alg("string");
 is this behaviour accepted
Yes.
 or should the compiler translate the first 
 case in the second?
No.
Mar 24
prev sibling next sibling parent Benjamin Schaaf <ben.schaaf gmail.com> writes:
On Sunday, 24 March 2019 at 12:45:13 UTC, Francesco Mecca wrote:
 https://run.dlang.io/is/zRcj59

 ```
 alias Alg = Algebraic!(int, string);

 void main()
 {
 	int n = 2;
     Alg value;

     value = n == 2 ? 2 : "string";
 }
 ```

 The original code used SumType but the effect is the same.

 I suppose that I could write the following:

 ```
     if(n == 2) value = 2;
     else value = "string";
 ```

 Is there a workaround for this that maintains a similar 
 syntactic structure?
 is this behaviour accepted or should the compiler translate the 
 first case in the second?
You can achieve the same thing by just constructing your algebraic type earlier: value = n == 2 ? Alg(2) : Alg("string");
Mar 25
prev sibling parent Michelle Long <HappyDance321 gmail.com> writes:
On Sunday, 24 March 2019 at 12:45:13 UTC, Francesco Mecca wrote:
 https://run.dlang.io/is/zRcj59

 ```
 alias Alg = Algebraic!(int, string);

 void main()
 {
 	int n = 2;
     Alg value;

     value = n == 2 ? 2 : "string";
 }
 ```

 The original code used SumType but the effect is the same.

 I suppose that I could write the following:

 ```
     if(n == 2) value = 2;
     else value = "string";
 ```

 Is there a workaround for this that maintains a similar 
 syntactic structure?
 is this behaviour accepted or should the compiler translate the 
 first case in the second?
You could make a Choose function: auto Ch(A,B)(bool c, A a, B b); Then value = Ch(n == 2, n, "string"); Not much different than value = (n == 2) ? Alg(2) : Alg("string"); except you don't have to write Alg all the time. The compiler should translate the first but that requires implicit conversion of any of the types T... to Algebraic!T... . Of course, that should be possible but is it?
Mar 25