---------- Forwarded message ---------- From: Vinod Parthasarathy <[email protected]> Date: 18 February 2011 12:46 Subject: Re: [Ilugc] Python list.reverse() [was: Re: [Fwd: [ilugcbe] Fifth Meeting Pics & Sri Shakthi Institute of Engineering and Technology updated in Open Street Map]] To: ILUG-C <[email protected]>
On 18 February 2011 10:49, openbala <[email protected]> wrote: > On Tue, Feb 15, 2011 at 2:25 PM, Noorul Islam K M <[email protected]> > wrote: > > openbala <[email protected]> writes: > > > >> On Mon, Feb 14, 2011 at 12:52 PM, Kenneth Gonsalves > >> <[email protected]> wrote: > >> > > > > What is wrong below? > > > > There is nothing wrong. Certain programming languages try to handle > certain things differently. > There is a new wave of languages that take immutability and > referential transparency very seriously. (please use your favourite > search engine to figure out what they are) > > The gist of immutability is that any operations on a data structure > should not change its data structure. (for e.g. java's String class is > immutable) > In python the "reverse()" method is mutating the list instead of > returning a new output. > > This is the output in ruby: > > $ numbers = [1, 2, 3, 4, 5] > => [1, 2, 3, 4, 5] > $ numbers.reverse > => [5, 4, 3, 2, 1] > $ numbers > => [1, 2, 3, 4, 5] > $ > > Note that the numbers list has not changed even after calling 'reverse' > method. > > The general consensus is that mutability is bad for programming. YMMV. > There is both a bad and a good side to mutability. Mutability can give rise to faster running programs than their immutable counterparts in certain situations. Space complexity is also reduced in mutable programs. The downside is that programming becomes error-prone and additional care is needed on the programmer's part. Vinod > > >>>> numbers = [1, 2, 3, 4, 5] > >>>> numbers.reverse() > >>>> numbers > > [5, 4, 3, 2, 1] > >>>> list.reverse(numbers) > >>>> numbers > > [1, 2, 3, 4, 5] > > > > Thanks and Regards > > Noorul > _______________________________________________ > ILUGC Mailing List: > http://www.ae.iitm.ac.in/mailman/listinfo/ilugc > _______________________________________________ ILUGC Mailing List: http://www.ae.iitm.ac.in/mailman/listinfo/ilugc
