Andre Artus:
It may not always be the case, but in my experience this often
leads to write-only code.
I'm pretty new to D, so I'm not quite up to speed with the
metaprogramming abilities, but I'm under the impression that
this is what mixin's are for.
MattCoder:
Well I'm not experienced too, but mixin's for what I know just
works in compiler time right?
But anyway it would be possible to write my own switch version
with mixin? I really would like to see this.
Matheus.
Yes, it takes any string that's valid D. I see people using it to
embed domain specific languages (e.g. PEG via PEGGED) so you
should easily be able to write a translator/preprocessor that
takes your switch and converts it to D code.
mixin("
switch (number)
{
default: // valid: ends with 'throw'
throw new Exception("unknown number");
common_entry:
// some common entry code
break;
common_exit:
// some common exit code
break;
case 3:
message ~= "three ";
break;
case 4:
message ~= "four ";
continue;
case 6:
message ~= "six ";
break;
}
");
The preprocessor could rewrite to this string:
"
switch (number)
{
case 3:
case 4:
case 6:
// some common entry code
break;
}
switch (number)
{
default: // valid: ends with 'throw'
throw new Exception("unknown number");
case 3:
message ~= "three ";
break;
case 4:
message ~= "four ";
continue;
case 6:
message ~= "six ";
break;
}
switch (number)
{
case 3:
case 4:
case 6:
// some common exit code
break;
}
"
**** I do not recommend anyone do this ****
The reason I would not recommend this is that it leads to brittle
code that is hard to debug and reason about.
The reason I use `switch`, and not `if` for the entry and exit
code is because these should only fire under the same conditions
as the cases in the original switch, otherwise you introduce hard
to find bugs in your code.
Once again, I do not recommend people doing this: my preference
is for code that makes the programmers intent clear and explicit.
