Re: Scope of $/

Limit the scope of the changed value of $/, by "local"izing it, and enclosing it in the smallest block possible:

{ # Add an enclosing block
   local $/= "\n\n\n";
   while(<>){
      local $/="\n"; # Reset to normal behaviour inside loop only
      my ($filename)=/^(\S+)/;
      my $text=reader::firstline($filename);
   }
} # End enclosing block.
[download]

This code avoids "Action at a distance", by making wierd settings in as limited a scope as possible.

This is not an optical illusion, it just looks like one.

Comment on Re: Scope of $/ Download Code

Replies are listed 'Best First'.
Re^2: Scope of $/ by BillKSmith (Monsignor) on May 26, 2016 at 13:29 UTC
A truly minimal scope solves the problem. `use strict; use reader; #$/= "\n\n\n"; while(do{local $/="\n\n\n"; $_=<>}){ my ($filename)=/^(\S+)/; my $text=reader::firstline($filename); }` [download] Update: Commented out original definition of $/. Bill	[reply] [d/l]
Re^3: Scope of $/ by NetWallah (Canon) on May 26, 2016 at 13:48 UTC
Applause, for a truly elegant solution ! I wish I had thought of that. This is not an optical illusion, it just looks like one.	[reply]
Re^2: Scope of $/ by Anonymous Monk on May 26, 2016 at 01:23 UTC
The enclosing block is just noise :) unless you give it a name	[reply]
Re^3: Scope of $/ by Marshall (Canon) on May 26, 2016 at 01:38 UTC
That is not true. No name is required. The {} set the scope of the local. For my demo below, I used an "our" variable, package scope. A Perl Global like $/ acts similar. You cannot localize a "my" variable. I guess you can think of a local var as sort of like creating a stack of that variable. The local statement is like a "push" and when you exit the scope of the local, that is like a "pop". Rough analogy, but that is descriptive of the behavior. `#!usr/bin/perl use warnings; use strict; our $x = 1; #a package variable { print "$x\n"; #prints 1 local $x = 99; print "$x\n"; #prints 99 } print "$x\n"; #prints 1, back to before the "local"` [download]	[reply] [d/l]
Re^4: Scope of $/ by Anonymous Monk on May 26, 2016 at 01:52 UTC
:) in the OPs program, having `{ local $/ ... }` on the outside doesn't change the behavior of the program, therefore no benefit is realized ... so the extra {local} is just extra typing (noise), unless you add a name, like `sub StdinTriElReader{ local $/ = "\n\n\n"; ... }` then its serves a purpose :D:D:)	[reply] [d/l] [select]
Re^5: Scope of $/ by Marshall (Canon) on May 26, 2016 at 01:55 UTC
Re^6: Scope of $/ by NetWallah (Canon) on May 26, 2016 at 05:51 UTC
Some notes below your chosen depth have not been shown here


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