On Feb 18, 9:52 pm, Gregory Ewing <greg.ew...@canterbury.ac.nz> wrote: > Steve Howell wrote: > > Python may not support the broadest notion of anonymous functions, but > > it definitely has anonymous blocks. You can write this in Python: > > > for i in range(10): > > print i > > print i * i > > print i * i * i > > There's a clear difference between this and a Ruby block, > however. A "block" in Ruby is implemented by passing a > callable object to a method. There is no callable object > corresponding to the body of a for-loop in Python. > > The important thing about Ruby blocks is not that they're > anonymous, but that they're concrete objects that can > be manipulated. >
Agreed. > The Ruby approach has the advantage of making it possible > to implement user-defined control structures without > requiring a macro facility. You can't do that in Python. > > However, there's something that Python's iterator protocol > makes possible that you can't do with a block-passing > approach. You can have multiple iterators active at once, > and pull values from them as an when required in the > calling code. Ruby's version of the iterator protocol > can't handle that, because once an iterator is started > it retains control until it's finished. > Is this still true or Ruby today? http://pragdave.blogs.pragprog.com/pragdave/2007/12/pipelines-using.html > Also, most people who advocate adding some form of > block-passing facility to Python don't seem to have > thought through what would happen if the block contains > any break, continue, return or yield statements. > For sure. It's certainly not clear to me how Ruby handles all those cases, although I am still quite new to Ruby, so it's possible that I just haven't stumbled upon the best explanations yet. > This issue was looked into in some detail back when there > was consideration of implementing the with-statement > by passing the body as a function. Getting these > statements to behave intuitively inside the body > turned out to be a very thorny problem -- thorny enough > to cause the block-passing idea to be abandoned in > favour of the current implementation. > I found these links in the archive...were these part of the discussion you were referring to? http://mail.python.org/pipermail/python-dev/2005-April/052907.html http://mail.python.org/pipermail/python-dev/2005-April/053055.html http://mail.python.org/pipermail/python-dev/2005-April/053123.html -- http://mail.python.org/mailman/listinfo/python-list
