Eric Strom (ASG) tag:blogs.perl.org,2009-11-03:/users/eric_strom_asg//1030 2011-12-18T01:55:36Z A blog about the Perl programming language Movable Type Pro 4.38 Introducing here tag:blogs.perl.org,2011:/users/eric_strom_asg//1030.2581 2011-12-18T01:19:53Z 2011-12-18T01:55:36Z I've just published the first release of the here module, a mechanism for safely inserting generated code into a compiling program. this can be used to write macros, cut down on boiler plate, and to implement new declarations, all without... Eric Strom (ASG) https://metacpan.org/author/ASG I've just published the first release of the here module, a mechanism for safely inserting generated code into a compiling program. this can be used to write macros, cut down on boiler plate, and to implement new declarations, all without ever having to parse any perl source code.

you operate on code as data, as you normally would when metaprogramming. then a call to use here $generated_code; injects that code into the compiling source

sub my_0 {map "my \$$_ = 0", @_} # a simple macro

use here my_0 qw(x y z);

results in perl compiling

my $x = 0; my $y = 0; my $z = 0;

and all of those variables are of course in scope after the use here line.

here on metacpan

an example module using here is here::declare, which provides compile time assignment to lexical variables as well as a shortcut for defining constants.

use here::declare;

use my '@foo' => [1, 2, 3];

results in perl compiling

my @foo; BEGIN {@foo = (1, 2, 3)}

or to define a constant:

use const2 DEBUG => 1;

which results in:

sub DEBUG () {1} our $DEBUG; BEGIN {*DEBUG = \DEBUG}

giving you both the $DEBUG constant scalar, and the DEBUG constant subroutine with one simple declaration.

feedback welcome.

]]> Introducing Begin::Declare tag:blogs.perl.org,2011:/users/eric_strom_asg//1030.2437 2011-11-13T22:03:34Z 2011-11-13T22:52:12Z While working on a module for source code injection, one of my example "macros" was one that allows you to declare and assign to a lexical variable at compile time, without having to write the variable names twice. That concept... Eric Strom (ASG) https://metacpan.org/author/ASG While working on a module for source code injection, one of my example "macros" was one that allows you to declare and assign to a lexical variable at compile time, without having to write the variable names twice. That concept more or less hijacked the conversation, and after some prodding from p5p to make the interface better, I've used Devel::Declare to add two new keywords to Perl, MY and OUR.

Here is the synopsis from the module:

don't you hate writing: 
my ($foo, @bar);
BEGIN {
    ($foo, @bar) = ('fooval', 1 .. 10);
}
when you should be able to write: 
MY ($foo, @bar) = ('fooval', 1 .. 10);
just use Begin::Declare; and you can.

The module lifts the computation of the rhs to compile time, as well as the assignment.

https://metacpan.org/module/Begin::Declare

]]>