http://d.puremagic.com/issues/show_bug.cgi?id=5543



--- Comment #20 from monarchdodra@gmail.com 2012-12-21 10:55:24 PST ---
(In reply to comment #18)
> (In reply to comment #16)
> 
> > Whereas if it threw to begin with you're forced to catch exceptions.
> 
> There is no perfect solution. Exceptions are safer than error codes because if you forget to test for a negative result, your program stops. On the other hand exceptions are less efficient, less handy to use in nothrow functions, and often require some try-catch wrapping.
> 
> In this enhancement request I was originally asking for an overload of to!(), this means a solution that throws exceptions when the input is wrong.
> 
> Efficiency is not a significant problem for me here because where I need to convert char digits to numerical digits with max efficientcy I use a '0' subtraction (or a vectorized version of it). So with this overload of to!() I was looking for safety.

I think a good solution is to accept having different semantics:

std.ascii.numericValue:
int numericValue(dchar c) safe nothrow pure; returns -1 on failure

std.uni.numericValue:
double numericValue(dchar c) safe pure; Throws on failure

If you are doing anything with unicode, the exception's overhead will be mostly
moot compared to the cost (I think). When operating with ASCII, then it's a
different ballgame (IMO).

That's my opinion anyways.

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