From: Mr Magpie <gazmcgheesubs@...>
Date: 2007-11-27T14:46:50+09:00
Subject: Re: FEATURE SUGGESTION: Accept default value for to_f and to_i

ara.t.howard wrote:
> On Nov 26, 2007, at 9:19 PM, Mr Magpie wrote:
> 
>> I believe exceptions are a performance drag, and these little  
>> functions
>> are often called thousands of times in a loop for processing input, so
>> I'd prefer to avoid a method that potentially causes exceptions. I  
>> think
> 
> 
> 
> but, unless you use #to_i exactly as it is now that is still the
> case?  with your suggestion this code
> 
>   'forty-two'.to_i(nil).abs
> 
> raises a NameError

Of course if you were chaining class-specific methods like abs you would 
have to use a default supporting that method.

> 
> so i think the point is that you either have
> 
>    'forty-two'.to_i.abs  # let zero be the default
> 
>     Integer 'forty-two'  # need to handle exceptions
> 
> and nothing in between because a to_i with a default that is non-
> numeric doesn't provide anything over the built-in Integer or Float.
> 

Yes, that is the choice at present.

The benefits my suggestion provides are :
1) allows an application specific default (of any type) to be supplied, 
reducing code required.
2) allows bad input to be unambigously detected, which (can distinguish 
"fds".to_i from "0".to_i)
3) because the result of to_i always evaluates to true, you can't do
     num.to_i ? 'valid int' : 'invalid int'
but with my sugestion you could do
     num.to_i(false) ? 'valid int' : 'invalid int'
4) would be a miniscule change to the existing optimised C unlike some 
monkey patch I could do
5) would avoid performance-sapping exceptions
6) would avoid expensive regular expressions
7) as a default parameter, wouldn't affect existing code.

I don't think any other approach satisfies all of the above.

Thanks for your reply and the code examples.

Regards,

magpie
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