From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2012-09-28T17:31:55+09:00
Subject: Re: calcaulation with unknown numbers of numbers and options fail

On Fri, Sep 28, 2012 at 10:18 AM, Roelof Wobben <rwobben@hotmail.com> wrote:
>
>
>> Date: Fri, 28 Sep 2012 17:09:08 +0900
>> From: jgabrielygalan@gmail.com
>> Subject: Re: calcaulation with unknown numbers of numbers and options fail
>> To: ruby-talk@ruby-lang.org
>
>>
>> On Fri, Sep 28, 2012 at 9:40 AM, Roelof Wobben <rwobben@hotmail.com>
>> wrote:
>> > Hello,
>> >
>> > I have this script:
>> >
>> > def calculate (options , *numbers)
>> > options << "add" if options.empty?
>> > numbers.inject(0) { |sum, number| sum + number } if options == "add"
>> > numbers.inject() { |sum, number| sum - number } if options == "subtract"
>> > end
>> >
>> > But now I see this output in Rubymonks :
>> >
>> > defaults to addtion when no option is specifiedNoMethodErrorundefined
>> > method
>> > `empty?' for 4:Fixnuminvoking calculate(4, 5, add: true) returns
>> > 9NoMethodErrorundefined method `empty?' for 4:Fixnuminvoking
>> > calculate(-10,
>> > 2, 3, add: true) returns -5NoMethodErrorundefined method `empty?' for
>> > -10:Fixnuminvoking calculate(0, 0, 0, 0, add: true) returns
>> > 0NoMethodErrorundefined method `empty?' for 0:Fixnum
>> >
>> > I think the problem is that I cannot take care that the right values are
>> > in
>> > the right variable.
>> >
>> >
>> > Anyone a tip how to solve this ?
>>
>> The options hash is the first parameter to your function, so pass it
>> as the first parameter:
>>
>> calculate({:add => true}, 4,5)
>>
>> and also, you shouldn't check options == "add", but options[:add] ==
>> true or just options[:add]
>>
>> Jesus.
>>
>
> Thanks,
>
> I can't change the function call because I try to learn  ruby by a
> interactive website.

Then you have to modify how you declare the function.

>
> I don't understand one remark. You say I shouldn't check the options
> =="add" .
> What I' trying to do is to add the word "add" to options if the options
> array = empty.
> So the function defaults to "add" when nothing is entered.

Options is not an array, it's a hash. but in any case it's never going
to be equal to "add". It will contain an element or a key "add".

Jesus.