What's the use of 'typeof','typeid','__traits','is' ?

[IchorDev]

On Sunday, 24 August 2025 at 03:13:38 UTC, David T. Oxygen wrote:
> The code above has simplified. It defines some simple classes.
>
> And now, I have a function:
> ```d
> import std.algorithm.searching;
> MyReal is_int_or_float(string inputs){
>     if(inputs.canFind('.'))
>         return new MyFloat(inputs);
>     else
>         return new MyInt(inputs);
> }
>
> ```

This would be a great use-case for `std.sumtype.SumType`:
```d
import std.sumtype: SumType, match;
alias Number = SumType!(double, long);

Number isIntOrFloat(string input){
	import std.algorithm.searching: canFind;
	import std.conv: to;
	if(input.canFind('.'))
		return Number(input.to!double());
	else
		return Number(input.to!long());
}

void main(){
	string input = "3.14";
	Number result = isIntOrFloat(input);
	import std.stdio: writeln;
	result.match!(
		(long x){ writeln("integral: ",x); },
		(double x){ writeln("floating: ",x); },
	);
}
```