John W . Krahn wrote: > On Friday 06 June 2003 13:22, Rob Dixon wrote: > > Katy Brownfield wrote: > > > On Fri, 6 Jun 2003 18:16:26 +0100, Rob Dixon > > > <[EMAIL PROTECTED]> > > > > > > wrote: > > > > John W. Krahn wrote: > > > > > Mark Anderson wrote: > > > > > > B) You should NEVER use map in a void context. map works > > > > > > very hard to build up it's return value, so there should be > > > > > > an assignment (=) operator to the left of your map call > > > > > > almost always, otherwise all of that work is wasted. > > > > > > > > > > I would never say NEVER as there are some situations where it > > > > > may be appropriate, just like there are some situations where > > > > > goto is appropriate. > > > > > > > > Sure, but I can't for the moment think of any difference between > > > > > > > > foreach (LIST) BLOCK > > > > or > > > > EXPRESSION foreach LIST > > > > > > > > and > > > > > > > > map BLOCK LIST > > > > or > > > > map EXPRESSION, LIST > > > > > > > > in void context. Any thoughts? > > > > > > Mark explained the difference. map has the overhead of building the > > > list that it returns. foreach doesn't. In Kevin's example a list > > > containing "01" .. "12" is created and never used. It's > > > inefficient. > > > > Thanks Katy, but John was saying that there were "some situations > > where it may be be appropriate [to use map in a void context]". I > > could think of none, since those constructs that I posted using > > 'foreach' seemed to do exactly the same thing without the overhead > > that you describe. I wondered if John (or anybody) knew of a > > difference that I didn't. > > Well, to quote Larry Wall[0] (you all know who he is don't you): > > "The argument against using an operator for other than its > primary purpose strikes me the same as the old argument that you > shouldn't have sex for other than procreational purposes. Sometimes > side effects are more enjoyable than the originally intended effect."
Sometimes, though, the side-effects spoil all the fun ;-) Rob -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
