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Re: BEGIN {} question

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September 10, 2022 16:00
Re: BEGIN {} question
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That is a nice summary of some differences among various Callables.


On Tue, Aug 30, 2022 at 09:34:01PM +0100, Richard Hainsworth wrote:
> Hi Todd,
> Long time no see.
> Re your 'keeper'. There is a reason why things are called the way they are
> in Raku (aka Perl6). BEGIN is NOT a special subroutine.
> BEGIN is a phaser. And it introduces a block. Blocks are not subroutines
> (subs). Even though blocks and subs (and methods and callables) are code
> related things, a sub can take a signature, but a block cannot. You can pass
> arguments to a block using pointy syntax, eg -> $x, %y {  ... }, which is
> why it is possible to do things like 'for %some-hash.kv -> $key, $value {
> .... }'. The 'for' takes a block, which can be pointy. 'for' does not take a
> special subroutine.
> But a sub can have a parameter list, eg., 'sub (Int $b where *>= 10) { say
> %b }; ' The 'where' bit means that the compiler will put in checks that $b
> is always greater-equal to 10. So subs are far far more than blocks.
> Also you cannot return from a block, but you can return from a sub.
> So, by putting in your keeper that BEGIN is a special subroutine, you are
> ignoring a whole world of Raku goodness, as well as making it difficult for
> yourself to understand other phasers.
> And talking of phasers, there are some really useful ones, like FIRST and
> LAST, that are in loops. So if you want something to happen first time in a
> loop, put it in FIRST { }.
> Also I see you are on the compile time whine again. When perl6 first became
> available as 'pugs', it did take FOREVER. Then as more of perl6 became
> implemented as rakudo, startup times became slower.
> Things changed when modules were precompiled. I really do not understand
> what you are talking about when you say you don't think precompile is useful
> everywhere.
> For example, when I write something that is called from the command line
> (for example in my raku-collection-raku-documentation distribution), I have
> a one-liner raku program 'RakuDoc' that just says 'use Collection::RakuDoc'.
> EVERYTHING else is in the module Collection::RakuDoc, all the MAIN
> subroutines, and stuff. That then only gets compiled once. So, the first
> time RakuDoc is called from the command line, there is a startup delay
> because the whole module is compiled. Every other time RakuDoc is called,
> its really so fast I don't notice a problem. Only the *one* line is compiled
> each time the program is called. All the rest is in precompiled form.
> Same with my Extractor program, which is in the raku-extraction module. This
> is a GUI program that takes the rakudoc (aka POD6) files and converts them
> into markdown. For example, I write the README's for my github repos as
> README.rakudoc, then use Extractor to turn it into a The result
> is far better because the rakudoc renderer I use (from my pod-render
> distribution) automatically collects all the headers and puts them into a
> Table of Contents. If you've tried to do a TOC in markdown, you know what a
> hassle it is.
> But Extractor is a GTK::Simple program. And GTK::Simple takes forever to
> precompile. But once done, I don't notice any startup time.
> And I change my software quite a lot, so every time I change something, yes,
> startup is slow the first time, but not the next time. Surely, you use a
> piece of software more than once.
> Compared to the OLD days, rakudo programs react like lightning. Design your
> software properly, and you wont - as a human - notice much of a delay.
> I think the startup complaint (not the compile time for something) has been
> effectively relegated to the days when rakudo was young. So whilst in the
> past I truly sympathised with your rants about compile times, I am now quite
> confused and I find sympathy hard to come by.
> Since you continue for ever to complain about 'compile' time issues, rather
> than startup times, I wonder whether the programs you write are massive
> monolithic lines of code with thousands of lines, much like most standard
> software when FORTRAN or COBOL were the high level languages, or whether you
> design things to make each section more manageable.
> If the programs you write to be run from the command line are thousands of
> lines long, then yes!! you will suffer!!! from long!!!! startup times
> because the program is re-compiled EVERY time. However, if you redesign the
> code, putting things into classes, roles, subroutines, and Raku-y goody
> things, you can push stuff into modules, and reduce your calling program to
> a single line.
> When you change your software, do you change every part of it every time? Or
> do you change some client related interface part? Put the interface part
> into one module, and the other more stable functionality into other modules.
> Then when you change the interface part, you dont change the other modules.
> They have already been compiled. So the first time you start up your
> program, only the section you have changed gets recompiled, not the entire
> monolith.
> By the way, I assume that you understand the Raku meaning of 'module', as
> opposed to a 'distribution'. When I write a large piece of software, I may
> have three or four different modules under the lib/ directory. The top level
> program (I try to make it one line only), uses one module, which then may
> use other modules, all of them in the same directory, under the lib/
> subdirectory. The distribution can then also contain simple tests under t/
> and development tests under xt/
> Regards,
> Richard
> On 30/08/2022 2:38 am, ToddAndMargo via perl6-users wrote:
> > On 8/28/22 15:58, ToddAndMargo via perl6-users wrote:
> > > Hi All,
> > > 
> > > I am thinking of using
> > > 
> > >     BEGIN {}
> > > 
> > > to fire up a splash screen (libnotify).
> > > 
> > > Question: is what happens between the brackets
> > > isolated from the rest of the code?   If I set
> > > variable values or declare variables, are they
> > > wiped out, etc.?
> > > 
> > > Many thanks,
> > > -T
> > > 
> > > 
> > 
> > 
> > 
> > My keeper on BEGIN.  That you for all the help
> > and tips!
> > 
> > 
> > 
> > Perl6: BEGIN {}
> > 
> > 
> > BEGIN is a special subroutine that runs at compile time.
> > It will see any code above it, such as variables and
> > imported modules, but not below it.
> > 
> > The idea is to run something at the start of compile before
> > the rest of compile completes.  A splash screen for example.
> > 
> > Perl 6's compile can take a very long time and users may not
> > realize it started and restart it several times.
> > 
> > Note that a space is required between `BEGIN and the `{}`
> > 
> > 
> > BEGIN {
> >    # Splash Screen
> > 
> >  ( my $ProgramName   = $?FILE ) ~~ s|.*"/"||;
> >    my Str $NotifyStr = "\nStarting $ProgramName\n";
> >    my Str $Icon      = "/home/linuxutil/Images/Info.png";
> >    my Str $Title     = "$ProgramName Splash Screen";
> >    my Str $Timeout   = "8";       # zenity = seconds
> > 
> >    # Note: zenity seems to not detach when run without a shell
> >    shell "zenity --info --title \"$Title\" --text \"$NotifyStr\"
> > --width=220 --timeout=$Timeout &";
> > }
> > 

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