Why exceptions for error handling is so important

[Martin Nowak via Digitalmars-d]

On Monday, 12 January 2015 at 21:11:44 UTC, Walter Bright wrote:
> On 1/12/2015 6:57 AM, Martin Nowak wrote:
>> The general solution in functional programming is error 
>> chaining.
>> An example, C is a function that reads in lines of a program 
>> and B is a function
>> that takes all those lines and counts words.
>> C will either return an error or lines and B will either 
>> immediately return that
>> error to A or convert the lines to word counts.
>> This works especially well with function chaining, because you 
>> can hide the
>> error propagation in a generic chaining method (called map).
>>
>> http://danielwestheide.com/blog/2012/12/26/the-neophytes-guide-to-scala-part-6-error-handling-with-try.html
>
>
> Yes, it still appears to be just a wrapper around returning two 
> values, and that has to be done for everything.

Yes, you wrap the return values, but it doesn't require to deal 
with errors in B.

> There's another downside to returning two values - extra code 
> is generated, and it consumes another register. It allocates 
> very scarce resources to rare cases - not a recipe for high 
> performance.

To defend that argument we'd first have to fix our own codegen.
https://issues.dlang.org/show_bug.cgi?id=12442

It doesn't really consume the register, because the error value 
is only needed directly after the call for a possible early 
return. But of course returning tuples can be less efficient.

OT!!
Reminds me of Manu's request for more efficient register return.
www.digitalmars.com/d/archives/digitalmars/D/Multiple_return_values..._160353.html