gistfile1.pl

# Rewriting this code (http://blogs.perl.org/users/ovid/2012/05/floating-point-rounding-errors.html) 
# for Perl 6: 

#!/usr/bin/env perl6

sub MAIN(Real $num where { 0 <= $_ < 1 }, Int :$bits = 32) {
    my $accumulator = 0;
    my $binary      = '';
    my @fractions;

    for 1 .. $bits -> $bit {
        my $denominator = 2 ** $bit;
        my $fraction    = 1 / $denominator;
        if $accumulator + $fraction <= $num {
            @fractions.push("1/$denominator");
            $binary ~= 1;
            $accumulator += $fraction;
        }
        else {
            $binary ~= 0;
        }
    }

    say qq:to"END";
    Original:  $num
    Bits:      $bits
    Fractions: {@fractions.join(" + ")}
    Binary:    $binary
    Result:    $accumulator
    END
}

=begin pod

If I run that with "./floating-point.p6 --bits=16 .3", I get the following:

    Original:  .3
    Bits:      16
    Fractions: 1/4 + 1/32 + 1/64 + 1/512 + 1/1024 + 1/8192 + 1/16384
    Binary:    0100110011001100
    Result:    0.299988

But if I run it with "./floating-point.p6 --bits=16 3" (note the `3` instead of `.3`), I get:

    Usage:
      ./floating-point.p6 [--bits=<Int>] <num> 

    shell returned 2

That's interesting because 3 is a Real number, but Perl 6 doesn't like it here. Also, Perl 6
is saying it's an Int in the error message.

I can get it to work if I use Rat instead of Real.

As an aside, I also can't figure out how to add a constraint to `$bits` requiring it to be
greater than 0, but still keep my default. Perl 6 always tells me the syntax is wrong.

    sub MAIN(Rat $num where { 0 <= $_ < 1 }, Int :$bits = 32 where { $_ > 0 } ) {
    #===SORRY!=== Error while compiling ./accum.p6
    #Missing block
    #at ./floating-point.p6:3
    #------>  where { 0 <= $_ < 1 }, Int :$bits = 32 ⏏where { $_ > 0 } ) {
    #    expecting any of:
    #        postfix
    #        infix stopper
    #        infix or meta-infix
    #
    #shell returned 1

Or the following, which tells me I can't modify an immutable block if I pass it .3, but
gives me a usage error if I pass it 3:

    sub MAIN(Rat $num where { 0 <= $_ < 1 }, Int :$bits where { $_ > 0 } = 32) {