From: Robert Klemme <bob.news@...>
Date: 2005-06-01T20:45:22+09:00
Subject: Re: array of object insert polices

dave wrote:
>> You should have a look at the thread:
>> Uniform vector class, inheriting from Array
>
>> Duck typing. Code that relies on ints in there will soon discover if
>> someone puts something non numeric in there.
>
> I had a look at Chapter 23 Duck Typing of Programming Ruby.
>
> I understand that i haven't to validate imput type, this let me
> a little bit lost.

This is what happens if you calculate the product on an array that
contains non numeric values:

13:21:05 [source]: irbs
>> values=[1,2,3,"4"]
=> [1, 2, 3, "4"]
>> product = values.inject(1) {|x,e|x*e}
TypeError: String can't be coerced into Fixnum
        from (irb):2:in `*'
        from (irb):2
        from (irb):2:in `inject'
        from (irb):2:in `each'
        from (irb):2:in `inject'
        from (irb):2


>
>> "Code that relies on ints will discover"
> ..and what if i write a class to calculate a productory and who uses
> this class see something like that on the monitor:
>
> "i'm an integer Hahhaaai'm an integer Hahhaaai'm an integer
> Hahhaaai'm an integer Hahhaaai'm an integer Hahhaaai'm an integer
> Hahhaaai'm an integer Hahhaaai'm an integer Hahhaaai'm an integer
> Hahhaaa"
>
> (he wronged to parse an imput file `integers: 3 3`).
>
>
> maybe unit tests can help me?

Definitely.

> help me, please.

Maybe you can be a bit more specific on what exactly you are trying to
achieve and then people can come up with more concrete answers.

Kind regards

    robert