Is there a way to replace Exception with as a macro in C?

Marco de Wild admin at
Tue Feb 19 06:21:43 UTC 2019

On Tuesday, 19 February 2019 at 05:50:04 UTC, yisooan wrote:
> I wonder there is the way as I said in the title. For instance,
> in C,
>> #define indexInvalidException Exception("The index is invalid")
>> /* Do something with the macro here */
>> if (false)
>>   indexInvalidException;
> This is allowed.
> But I want to do the exact same thing in D. I have already 
> tried some expressions with alias? but it doesn't work.
>> alias indexInvalidException = Exception("The index is 
>> invalid");
>> /* Use the alias in somewhere */
>> if (false)
>>   throw new indexInvalidException;
> Would you help me, please?

Alias is just a nickname for a symbol (i.e. alias string = 
immutable(char)[];) and lets you refer to that symbol with the 
nickname. You can't supply runtime parameters (like constructor 
parameters), but you can give compile-time template parameters 
(as the result of applying those parameters is a symbol rather 
than a value). Macros on the other hand, do a textual 
replacement, i.e. they alter the source code that goes into the 

Depending on how brief you want to make your code, you can either 
use classic inheritance
class IndexInvalidException : Exception
         super("The index is invalid")

or, closest as you can get to macros:
enum throwNewIndexInvalidException = `throw new Exception("The 
index is invalid");`;

void main()

String mixins transform a string into an expression, and paste 
the expression wherever it is mixed in. It gets precompiled 
rather than substituted in the source code. This means it's best 
to have the whole line into a string, instead of individual parts 
(you can't have a mixin with just `Exception("The index is 
invalid")` for example).

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