Ruby Procs, return & yield semantics

procs.rb

require 'rubygems'
require 'expectations'

Expectations do

expect(1){ proc { |a| a }.call(1) }
expect([1, 2]){ proc { |a| a }.call(1, 2) } #fails
expect(1){ proc { |a, b| a }.call(1, 2) }

expect(1){ Proc.new { |a| a }.call(1) }
expect([1, 2]){ Proc.new { |a| a }.call(1, 2) } #fails
expect(1){ Proc.new { |a, b| a }.call(1, 2) }

def foo
    x = proc { return :block }
    x.call()
    return :method
end

expect foo().to.be == :method #fails

def bar
    x = Proc.new { return :block }
    x.call()
    return :method
end

expect bar().to.be == :block

=begin
def boo
    yield :block
    return :method
end

# does not compile as return not allowed in implicit block
expect boo{ |a| return a }.to.be == :method

def baz &block
    block.call(:block)
    return :method
end

# not even when block param is explicitly declared in method
expect baz{ |a| return a }.to.be == :block
=end

end

Compare with Paul Cantrell's snippet.