CODEWITHSUNDEEP
rubyperl
Neil H Watson
Neil H Watson

Reputation: 1070

Perl like anonymous subroutines in ruby

I'm new to ruby and trying to duplicate this perl, that calls anonymous subroutines, in ruby:

#!/usr/bin/perl

use strict;
use warnings;
use feature 'say';

# Make a reference to a subroutine
my $codes = {
   one => sub {
      say "This is code block one";
      say "And this is code block one's line two"
   },
};

for my $next_code ( keys %{ $codes } ) {
   # Execute anonymous subroutine
   &{ $codes->{ $next_code } };
}

I tried this:

#!/usr/bin/ruby -w

codes = {
   one: puts "This is code block one"
        puts "And this is code block one's line two",
 }
codes.each do |next_code|
   next_code
end

But, I get syntax errors. Is this possible, or is there another preferred ruby way?

UPDATE: Yes, this is like a dispatch table. I store code in a hash and run that code later.

Upvotes: 3

Views: 132

Answers (1)

Jörg W Mittag
Jörg W Mittag

Reputation: 369428

Ruby has Procs as anonymous first-class subroutine objects. Procs can be created by passing a block to Proc::new, Kernel#proc, or Kernel#lambda, or with the "stabby lambda" lambda literal syntax.

#!/usr/bin/env ruby

# Make a reference to a subroutine
codes = {
  one: -> {
    puts "This is code block one"
    puts "And this is code block one's line two"
  }
}

codes.each do |name, code|
  # Execute anonymous subroutine
  code.()
end

The most widely-used form of anonymous code block in Ruby is a construct called a block, which is actually not an object, but just a syntactic construct. Every method in Ruby takes exactly one optional block argument, which can be passed either in curly braces or using a do/end keyword pair after the normal method arguments. You can see a block in action in the code above, being passed to the Hash#each iteration method.

In case you are interested, here is a small toy project of mine that demonstrates the use of first-class closures in a variety of languages, including Perl5 and Perl6, Ruby, PHP, Python, ECMAScript, Smalltalk, Clojure, Scheme, and many others: http://joergwmittag.github.io/lambdaconscarcdr/

Upvotes: 7

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