2008/1/22, Jeff Pang <[EMAIL PROTECTED]>: > > > > -----Original Message----- > >From: Jenda Krynicky <[EMAIL PROTECTED]> > >Sent: Jan 23, 2008 12:59 AM > >To: beginners-list <beginners@perl.org> > >Subject: Re: about the dot > > > >From: Jeff Pang <[EMAIL PROTECTED]> > >> I'm a little confused by perl's dot operator.for example, > >> > >> $ perl -le 'print 3 . 4 ' > >> 34 > >> $ perl -le 'print 3.4 ' > >> 3.4 > >> > >> these two commands got different results. > >> > >> who says Perl interpreter will ignore the blackspace around an > operator? I saw it doesn't here. > >> Ok you may say 3.4 is a float not a statement with '.' operation, but > this case really make people confused. > > > >As far as I can tell you are the first to get confused. > > > >I mean if the compiler sees a digit it knows a numerical literal > >starts. So it reads as much as it can that still matches the > >definition of numberical literal and then looks for an operator or > >end of statement or end of block or closing brace or ... > > > >3.4 whole matches so it is treated as such. And since spaces are not > >allowed withing numerical literals as soon as perl encounters a space > >the literal is considered complete and perl starts to look for the > >next thing. > > > >In either case it is what it looks like. 3.4 looks like a float so it > >is float. 3 . 4 doesn't look like a single float. It looks like two > >integers with some operator. And that's what it is. > > > > Ok thanks. > But how about this case? why it can't work as we think? > > $ perl -le 'print 3.4 .3. 4' > Number found where operator expected at -e line 1, near "3. 4" > (Missing operator before 4?) > syntax error at -e line 1, near "3. 4" > Execution of -e aborted due to compilation errors. > > > and why this can work? > > $ perl -le 'print 3.4 .3 .4' > 3.434 > > > in the first case, what rules let perl think the last dot is not an > operator but a part of the float? > > Regards, > Jeff Pang > > -- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > http://learn.perl.org/
Hi 3.4 is a numbre in the c style or native floating point numbers but .3 .4 not in these cases are operator . (dot) and 3 (character '3') more of this on perlnumber cheers
