From: "prijutme4ty (Ilya Vorontsov)" <prijutme4ty@...>
Date: 2012-10-01T18:31:14+09:00
Subject: [ruby-core:47761] [ruby-trunk - Feature #7091] Object#puts_to


Issue #7091 has been updated by prijutme4ty (Ilya Vorontsov).


Don't you feel that mixing function call and method-chain is ugly? This was the main reason why I proposed this method, not inability to do this.
In case that expression is full of curl-braces and so on, additional level of "brace-deepness" is much worse that additional method in chain. Compare a real-life example (discreting a matrix):

File.write('matrix.out', File.readlines('matrix.in').map{|line| line.strip.split.map(&:to_f).map(&:round).join("\t")})

File.readlines('matrix.in').map{|line| line.strip.split.map(&:to_f).map(&:round).join("\t")}.puts_to('matrix.out')

Both expressions are rather complex, but in the first form main operations are hidden inside braces of write or puts function. Also here input and output appear in adjacent expressions. In the second form main part of calculations is not shaded by output code. Also one can trace path of data from input file through calculations to output file.
----------------------------------------
Feature #7091: Object#puts_to
https://bugs.ruby-lang.org/issues/7091#change-29818

Author: prijutme4ty (Ilya Vorontsov)
Status: Rejected
Priority: Normal
Assignee: 
Category: 
Target version: 


I suggest a new method Object#puts_to(io_or_filename) (or BasicObject#puts_to)

It's usual that one-two-three-line scripts have big chains like
readlines.sort.map{...}.select{...} and so on and after you wrote such a monstruous expression to process input, you understand that you should output it. If script's written offhand, you wouldn't create a new variable just to use it at next line, so you write smth like

puts( readlines.sort.map{...}.select{...} )
or at least
readlines.sort.map{...}.select{...}.tap{|x| puts x}

It looks ugly and isn't readable. Thing get even worse when you are writing object info a file:
File.open('file.txt','w'){|f| f.puts( readlines.sort.map{...}.select{...} ) }

I write such constructions many times a day, just because my scripts are usually used once or twice and I can't waste my time to make this more clear.
Instead of such a pasta-code, one can make smth like this:

readlines.sort.map{...}.select{...}.puts_to
readlines.sort.map{...}.select{...}.puts_to($stderr)
readlines.sort.map{...}.select{...}.puts_to('')
readlines.sort.map{...}.select{...}.puts_to(filename:'', append:true)

Implementation can be smth like this:

class Object
  def puts_to(io_or_filename = $stdout)
    if io_or_filename.respond_to?(:puts)
      io_or_filename.puts(self)
    else
      case io_or_filename
      when String
        File.open(io_or_filename,'w'){|f| f.puts self }
      when Hash
        File.open(io_or_filename[:filename],io_or_filename[:append] ? 'a' : 'w'){|f| f.puts self }
      end
    end
  end
end


Or may be Hash-syntax for append-mode should be written simply as two arguments:
obj.puts_to('file.txt', true)


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