Rails - Feb 2013 - Calling a function: one space difference between failing and succeeding

I have a function defined as follows:

def download_file (url1, url2, file1, file_age_max_hours)
    puts (url1)
    puts (url2)
    puts (file1)
    puts (file_age_max_hours)
end

The following command works:
download_file("Hello", "World", "Rubyists", 34)

The following command fails:
download_file ("Hello", "World", "Rubyists", 34)

The only difference is the space before the "(".  Why is the presence
or
absence of this space so significant?  This was never a problem for me in 
Python.  (On the other hand, I quickly learned to NEVER use tabs to indent 
when programming in Python.) 

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On 20 February 2013 17:57, Jason Hsu, Android developer
<jhsu802701-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I have a function defined as follows:
>
> def download_file (url1, url2, file1, file_age_max_hours)
>     puts (url1)
>     puts (url2)
>     puts (file1)
>     puts (file_age_max_hours)
> end
>
> The following command works:
> download_file("Hello", "World", "Rubyists",
34)
>
> The following command fails:
> download_file ("Hello", "World", "Rubyists",
34)
>
> The only difference is the space before the "(".  Why is the
presence or
> absence of this space so significant?  This was never a problem for me in
> Python.  (On the other hand, I quickly learned to NEVER use tabs to indent
> when programming in Python.)
Because this is Ruby not Python.  My understanding of why this is so
(which may be wrong or at least incomplete) is because you do not need
the parentheses at all, so you could say
download_file   "Hello", "World", "Rubyists", 34
so if you have a space and a "(" then the space starts the parameter
list and then along comes a "(" which may now have a different
meaning, dependant on context.  So the best thing is just to remember
not to put a space after the method name if you are using parentheses.

Colin

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On Wed, Feb 20, 2013 at 3:25 PM, Colin Law
<clanlaw-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
wrote:
> On 20 February 2013 17:57, Jason Hsu, Android developer
> <jhsu802701-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> I have a function defined as follows:
>>
>> def download_file (url1, url2, file1, file_age_max_hours)
>>     puts (url1)
>>     puts (url2)
>>     puts (file1)
>>     puts (file_age_max_hours)
>> end
>>
>> The following command works:
>> download_file("Hello", "World",
"Rubyists", 34)
>>
>> The following command fails:
>> download_file ("Hello", "World",
"Rubyists", 34)
>>
>> The only difference is the space before the "(".  Why is the
presence or
>> absence of this space so significant?  This was never a problem for me
in
>> Python.  (On the other hand, I quickly learned to NEVER use tabs to
indent
>> when programming in Python.)
>
> Because this is Ruby not Python.  My understanding of why this is so
> (which may be wrong or at least incomplete) is because you do not need
> the parentheses at all, so you could say
> download_file   "Hello", "World", "Rubyists",
34
> so if you have a space and a "(" then the space starts the
parameter
> list and then along comes a "(" which may now have a different
> meaning, dependant on context.  So the best thing is just to remember
> not to put a space after the method name if you are using parentheses.
the space + () creates a new closure and that closure causes an error
because you have a bunch of commas outside of context.  Colin is
right, I just wanted to elaborate that it creates a new closure.

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