proc-object

A method that applies self to a proc

由 落花浮王杯 提交于 2020-01-16 11:48:23
问题 I want to have a method defined on Object that takes a block and applies the receiver to the block. An implementation will be like the following: class Object def apply ≺ pr.call(self) end end 2.apply{|x| x * 3} # => 6 Is there already a standard way to do this or a well known library that has a method with similar use? If so, I didn't want to reinvent the wheel. It happens to me very often that, I have a method that takes an optional block, and when there is no block, I want to return

Ruby - lambda vs. Proc.new [duplicate]

由 孤街浪徒 提交于 2019-12-18 12:47:10
问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: What's the difference between a proc and a lambda in Ruby? When run this Ruby code: def func_one proc_new = Proc.new {return "123"} proc_new.call return "456" end def func_two lambda_new = lambda {return "123"} lambda_new.call return "456" end puts "The result of running func_one is " + func_one puts "" puts "The result of running func_two is " + func_two The result that I get is as follows: The result of

How do I marshal a lambda (Proc) in Ruby?

由 冷暖自知 提交于 2019-12-18 04:32:09
问题 Joe Van Dyk asked the Ruby mailing list: Hi, In Ruby, I guess you can't marshal a lambda/proc object, right? Is that possible in lisp or other languages? What I was trying to do: l = lamda { ... } Bj.submit "/path/to/ruby/program", :stdin => Marshal.dump(l) So, I'm sending BackgroundJob a lambda object, which contains the context/code for what to do. But, guess that wasn't possible. I ended up marshaling a normal ruby object that contained instructions for what to do after the program ran.

What are the advantages of proc functions to methods

由 冷暖自知 提交于 2019-12-14 00:33:45
问题 I was solving some problems on Project Euler and I mentioned that I always wrap short methods in proc functions. I asked myself " Why? ". The answer was " I don't know. Maybe because it is short? ". So what are the advantages of proc functions to ordinary methods except that they are short :) # Proc is_prime = proc{|number| !((number%2 == 0) || (3..Math.sqrt(number).to_i).step(2).any?{|n| (number%n).zero?})} # Ordinary method def is_prime(number) !((number%2 == 0) || (3..Math.sqrt(number).to

Inconsistency of arity between Hash.each and lambdas

由 六眼飞鱼酱① 提交于 2019-12-12 07:20:45
问题 I lifted the following example from Josh Susser def strip_accents params thunk = lambda do |key,value| case value when String then value.remove_accents! when Hash then value.each(&thunk) end end params.each(&thunk) end when I put it in the the rails console (irb), and call it with a hash, I get the following: ruby-1.9.2-p136 :044 > `ruby --version` => "ruby 1.9.2p136 (2010-12-25 revision 30365) [i686-linux]\n" ruby-1.9.2-p136 :045 > strip_accents({:packs=>{:qty=>1}}) ArgumentError: wrong

What are the advantages of proc functions to methods

由 坚强是说给别人听的谎言 提交于 2019-12-05 21:48:40
I was solving some problems on Project Euler and I mentioned that I always wrap short methods in proc functions. I asked myself " Why? ". The answer was " I don't know. Maybe because it is short? ". So what are the advantages of proc functions to ordinary methods except that they are short :) # Proc is_prime = proc{|number| !((number%2 == 0) || (3..Math.sqrt(number).to_i).step(2).any?{|n| (number%n).zero?})} # Ordinary method def is_prime(number) !((number%2 == 0) || (3..Math.sqrt(number).to_i).step(2).any?{|n| (number%n).zero?}) end Being able to pass them around and to store them in data

Why does the break statement in ruby behave differently when using Proc.new v. the ampersand sign?

由 核能气质少年 提交于 2019-12-01 00:59:21
问题 The break statement for blocks (as per The Ruby Programming Language) is defined as follows: it causes the block to return to its iterator and the iterator to return to the method that invoked it. Therefore when the following code is run, it results in a LocalJumpError. def test puts "entering test method" proc = Proc.new { puts "entering proc"; break } proc.call # LocalJumpError: iterator has already returned puts "exiting test method" end test While the following code does not throw a

Ruby: convert proc to lambda?

由 我们两清 提交于 2019-11-30 06:32:34
问题 Is it possible to convert a proc-flavored Proc into a lambda-flavored Proc? Bit surprised that this doesn't work, at least in 1.9.2: my_proc = proc {|x| x} my_lambda = lambda &p my_lambda.lambda? # => false! 回答1: This one was a bit tricky to track down. Looking at the docs for Proc#lambda? for 1.9, there's a fairly lengthy discussion about the difference between proc s and lamdba s. What it comes down to is that a lambda enforces the correct number of arguments, and a proc doesn't. And from

How do I marshal a lambda (Proc) in Ruby?

由 一笑奈何 提交于 2019-11-29 05:31:59
Joe Van Dyk asked the Ruby mailing list : Hi, In Ruby, I guess you can't marshal a lambda/proc object, right? Is that possible in lisp or other languages? What I was trying to do: l = lamda { ... } Bj.submit "/path/to/ruby/program", :stdin => Marshal.dump(l) So, I'm sending BackgroundJob a lambda object, which contains the context/code for what to do. But, guess that wasn't possible. I ended up marshaling a normal ruby object that contained instructions for what to do after the program ran. Joe You cannot marshal a Lambda or Proc. This is because both of them are considered closures, which

How do you stringize/serialize Ruby code?

由 怎甘沉沦 提交于 2019-11-29 03:19:42
I want to be able to write a lambda/Proc in my Ruby code, serialize it so that I can write it to disk, and then execute the lambda later. Sort of like... x = 40 f = lambda { |y| x + y } save_for_later(f) Later, in a separate run of the Ruby interpreter, I want to be able to say... f = load_from_before z = f.call(2) z.should == 42 Marshal.dump does not work for Procs. I know Perl has Data::Dump::Streamer , and in Lisp this is trivial. But is there a way to do it in Ruby? In other words, what would be the implementation of save _ for _ later ? Edit : My answer below is nice, but it does not
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