From: Tom Sawyer <transami@...>
Date: 2003-02-06T22:19:53+09:00
Subject: Re: %L, %l revisited

On Thursday 06 February 2003 04:45 am, Dossy wrote:
> You ought to read this very well-written article on here-docs, written
> by Randal Schwartz:
>
> Unix Review Column 12 (January 1997)
> http://www.stonehenge.com/merlyn/UnixReview/col12.html

good little read, thanks. did you catch the line:

	"Sorry for the strange indentation, but here-docs have significant leading 
whitespace. Grr."

;-)

> My personal favorite and not commonly known feature of here-docs:
>
> irb(main):015:0> puts <<`SHELL`
> irb(main):016:0`   for i in *; do
> irb(main):017:0`   echo $i
> irb(main):018:0`   done
> irb(main):019:0` SHELL
> [..my files snipped..]
> nil

very cool too. execute and build dynamic shell scripts. does #{x} work within 
`shell` form of heres?

> Here-docs improve clarity, usually.

well, in the simple cases i think yes. but like this:

for (<<'EOF' =~ /(.+)/g) {
        fredf:Fred Flintstone:$25
        barneyb:Barney Rubble:$100
        bettyb:Betty Rubble:$0.05
        EOF
                ($email, $person, $owe) = split /:/;
                print <<EOM;
        ## mail for $person
        mail -s "$person, you deadbeat!" $email <<INPUT
        Hey, $person, you owe us $owe!
        Pay up, or else!
        INPUT
        ## end of mail for $person
        EOM
}

my eyes start to blur. just for comparision (psuedo):

$pl = %l|fredf:Fred Flintstone:$25
             |barneyb:Barney Rubble:$100
             |bettyb:Betty Rubble:$0.05

for ($pl =~ /(.+)/g) { 
	($email, $person, $owe) = split /:/;
	print %L|## mail for $person
                      |mail -s "$person, you deadbeat!" $email <<INPUT
                      |Hey, $person, you owe us $owe!
                      |Pay up, or else!
                      |INPUT
                      |## end of mail for $person
}

a little better i think, but still a bit blury b/c it's shell AND Perl! :-)

> Yes, that old.

> Apparently, the improvement of "<<-word" here-docs that strip leading
> tabs only came two years later, in 1981:
>
>     o here document with trailing dash "<<-" strips leading tabs

well, that's interesting in its own right. the <<- is not only to allow the 
EOT (or what have you) to be indented, but to remove all initial tabs in the 
text itself. curious ruby dosen't do. i wonder if perl does....duh! first 
quote of this email; it would indicate perl doesn't either. that might offer 
an more elegant solution for HERE docs at least:

puts <<-TOHERE
		this is
		untabed
		TOHERE

this is
untabbed

puts <<-TOHERE
		this is
		untabed
	TOHERE

	this is
	untabbed

of course don't ask me what would happen if one did:

puts <<-TOHERE
		this is
		untabed
			TOHERE

-- 
tom sawyer, aka transami
transami@transami.net