Re: reduce, map, :+ and :upcase as blocks and symbols as arguments

From	Fernando Basso <fernanodobasso.br@gmail.com>
Newsgroups	comp.lang.ruby
Subject	Re: reduce, map, :+ and :upcase as blocks and symbols as arguments
Date	2018-07-05 07:01 -0300
Organization	Netfront http://www.netfront.net/
Message-ID	<phkq9q$e31$1@adenine.netfront.net> (permalink)
References	<ph29i8$1alc$1@adenine.netfront.net> <fq5rr6Ff076U1@mid.individual.net>

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On 05/07/2018 03:23, Robert Klemme wrote:
> On 28.06.2018 11:25, Fernando Basso wrote:
>> Why does `reduce' work passing both `&:+' _and_ `:+', but `map' seems to
>> accept only `&:upcase' (but not `:upcase`)?
>>
>>>> (1..5).reduce(:+)
>> => 15
>>>> (1..5).reduce(&:+)
>> => 15
>>>> ['x', 'y', 'z'].map(:upcase)
>> ArgumentError: wrong number of arguments (given 1, expected 0)
>> from (pry):3:in `map'
>>>> ['x', 'y', 'z'].map(&:upcase)
>> => ["X", "Y", "Z"]
>>
>> Docs for `Enumerable#reduce' say:
>>
>> ""
>> Combines all elements of enum by applying a binary
>> operation, specified by a block or a symbol that names a
>> method or operator.
>> ""
>>
>> Docs `Enumerable#map' say:
>>
>> ""
>> Returns a new array with the results of running block once
>> for every element in enum.
>> ""
>>
>> So, is that `reduce' takes both a block and a symbol, while map takes
>> only a block?
> 
> Yes.

Okay. I'm glad I more or less got that from reading the docs.

> 
>> And if so, is that some Ruby inconsistency?
> 
> Yes.

Okay, I'm yet to see very consistent language, actually. It looks like
all of them have some quirk spots.

> 
> Actually I am surprised that #reduce / #inject accepts a single Symbol.
> But these methods have some subtleties in argument handling anyway, so
> maybe I should not be surprised.

Indeed, makes sense. Thanks.

With gratitude,
Fernando

> Kind regards
> 
>     robert
> 
>

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reduce, map, :+ and :upcase as blocks and symbols as arguments Fernando Basso <fernanodobasso.br@gmail.com> - 2018-06-28 06:25 -0300
  Re: reduce, map, :+ and :upcase as blocks and symbols as arguments Robert Klemme <shortcutter@googlemail.com> - 2018-07-05 08:23 +0200
    Re: reduce, map, :+ and :upcase as blocks and symbols as arguments Fernando Basso <fernanodobasso.br@gmail.com> - 2018-07-05 07:01 -0300

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