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comp.lang.ruby

Re: ruby equivalent PHP function is_numeric?

Gavin Kistner

11/17/2006 6:23:00 PM

From: jason.dusek@gmail.com [mailto:jason.dusek@gmail.com] On
> It really is too bad that String.to_f does not throw an exception - or
> at least return NaN - when the string is not a number.

Float( mystring )
does raise an exception, however.
2 Answers

Giles Bowkett

11/17/2006 7:31:00 PM

0

On 11/17/06, Gavin Kistner <gavin.kistner@anark.com> wrote:
> From: jason.dusek@gmail.com [mailto:jason.dusek@gmail.com] On
> > It really is too bad that String.to_f does not throw an exception - or
> > at least return NaN - when the string is not a number.
>
> Float( mystring )
> does raise an exception, however.

hmm, I'm new to Ruby too, so I tried this in irb.

irb(main):001:0> muppet = "3.14"
=> "3.14"
irb(main):002:0> muppet.to_f
=> 3.14
irb(main):003:0> muppet
=> "3.14"
irb(main):004:0> penguin = "banana"
=> "banana"
irb(main):005:0> penguin.to_f
=> 0.0
irb(main):006:0> Float(muppet)
=> 3.14
irb(main):007:0> Float(penguin)
ArgumentError: invalid value for Float(): "banana"
from (irb):7:in `Float'
from (irb):7
from :0
irb(main):008:0> exit

I think String#to_f should probably throw an exception too. actually,
I think whatever the behavior of the two methods is, it should
probably be the same in either case. otherwise you end up with the
kind of API where you have thirty different methods of doing the same
thing, but only two of them work, and of the two that work, neither of
them work all the time.

it's like, you have Perl's "more than one way to do it" and Python's
"only one way to do it" and you have to be careful about letting these
creatures mate, it's kind of a mad scientist situation, you could end
up with a monster like, "there's more than one way to do it, but only
one of them actually works, and which one it is varies unpredictably."

--
Giles Bowkett
http://www.gilesg...

Logan Capaldo

11/19/2006 6:39:00 PM

0

On Sat, Nov 18, 2006 at 04:31:14AM +0900, Giles Bowkett wrote:
> On 11/17/06, Gavin Kistner <gavin.kistner@anark.com> wrote:
> >From: jason.dusek@gmail.com [mailto:jason.dusek@gmail.com] On
> >> It really is too bad that String.to_f does not throw an exception - or
> >> at least return NaN - when the string is not a number.
> >
> >Float( mystring )
> >does raise an exception, however.
>
> hmm, I'm new to Ruby too, so I tried this in irb.
>
> irb(main):001:0> muppet = "3.14"
> => "3.14"
> irb(main):002:0> muppet.to_f
> => 3.14
> irb(main):003:0> muppet
> => "3.14"
> irb(main):004:0> penguin = "banana"
> => "banana"
> irb(main):005:0> penguin.to_f
> => 0.0
> irb(main):006:0> Float(muppet)
> => 3.14
> irb(main):007:0> Float(penguin)
> ArgumentError: invalid value for Float(): "banana"
> from (irb):7:in `Float'
> from (irb):7
> from :0
> irb(main):008:0> exit
>
> I think String#to_f should probably throw an exception too. actually,
> I think whatever the behavior of the two methods is, it should
> probably be the same in either case. otherwise you end up with the
> kind of API where you have thirty different methods of doing the same
> thing, but only two of them work, and of the two that work, neither of
> them work all the time.
>
> it's like, you have Perl's "more than one way to do it" and Python's
> "only one way to do it" and you have to be careful about letting these
> creatures mate, it's kind of a mad scientist situation, you could end
> up with a monster like, "there's more than one way to do it, but only
> one of them actually works, and which one it is varies unpredictably."
>
Nah. Integer( ) works the same way. Think about Float( ) and Integer( )
vs. to_i and to_f being sort of like #to_int vs. #to_i. to_i is like, I
want an int out of this, whether this string is an int or not. Integer
is like "I have an integer, it just happens to be current represented as
a string."
> --
> Giles Bowkett
> http://www.gilesg...