How to avoid throwing an exceptions for a built-in function?

[Jordan Wilson via Digitalmars-d-learn]

On Thursday, 11 May 2017 at 18:07:47 UTC, H. S. Teoh wrote:
> On Thu, May 11, 2017 at 05:55:03PM +0000, k-five via 
> Digitalmars-d-learn wrote:
>> On Thursday, 11 May 2017 at 17:18:37 UTC, crimaniak wrote:
>> > On Wednesday, 10 May 2017 at 12:40:41 UTC, k-five wrote:
>> ---------------------------------------------------------
>> > try this: 
>> > https://dlang.org/phobos/std_exception.html#ifThrown
>> 
>> 
>> 
>> Worked. Thanks.
>> 
>> import std.stdio;
>> import std.conv: to;
>> import std.exception: ifThrown;
>> 
>> void main( string[] args ){
>> 
>> 	string str = "string";
>> 	int index = to!int( str ).ifThrown( 0 ); // if an exception 
>> was thrown, it
>> is ignored and then return ( 0 );
>> 	writeln( "index: ", index );	// 0
>> }
>
> Keep in mind, though, that you should not do this in an inner 
> loop if you care about performance, as throwing / catching 
> exceptions will incur a performance hit.  Outside of inner 
> loops, though, it probably doesn't matter.
>
>
> T

This reason is why I sometimes use isNumeric if I have heaps of 
strings I need to convert,  to reduce exceptions. So something 
like:
int index = (str.isNumeric) ? to!int(str).ifThrown(0) : 0;

Jordan