--- Tom Phoenix <[EMAIL PROTECTED]> wrote:
> On 9/10/06, chen li <[EMAIL PROTECTED]> wrote: > > > So map function returns the transformed or changed > > elements but not the original ones and grep still > > returns the original ones? > > The only thing grep can return are the elements of > the original list, > but it generally doesn't return all of them. > > > For example after certain > > operation A changes to B, in case of map the > return > > is B but in case grep the return is still A. Is > that > > right? > > What do you mean by "A changes to B"? It sounds as > if you're talking > about a map expression that takes A (in $_) as input > and returns B > (the value of the map expression). In that case, B > is a list > expression, so it may include any number of > elements, even zero. But > from what you've written, I think you're thinking of > the case where B > is a single value. That is to say, your map > expression turns one input > value into one output value. > > If you were to use that same expression in grep, it > would be evaluated > in scalar context. The scalar context value of an > expression may be > unrelated to the value than it would give in list > context. In grep, > it's a Boolean context, which is a special kind of > scalar context. If > the grep expression returns a true value, the > original element is > included; otherwise it's not. > > Cheers! > > --Tom Phoenix > Thanks for the explanations. I think I now finally get them. Li __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] <http://learn.perl.org/> <http://learn.perl.org/first-response>
